fa2e614 test: Fix off-by-one in mockscheduler test RPC (MarcoFalke)

Pull request description:

  Fixes:

  ```
  fuzz: scheduler.cpp:83: void CScheduler::MockForward(std::chrono::seconds): Assertion `delta_seconds.count() > 0 && delta_seconds < std::chrono::hours{1}' failed.
  ==1059066== ERROR: libFuzzer: deadly signal
      #0 0x558f75449c10 in __sanitizer_print_stack_trace (/root/fuzz_dir/scratch/fuzz_gen/code/src/test/fuzz/fuzz+0x5fec10)
      #1 0x558f753f32b8 in fuzzer::PrintStackTrace() fuzzer.o
      #2 0x558f753d68d3 in fuzzer::Fuzzer::CrashCallback() fuzzer.o
      #3 0x7f4a3cbbb3bf  (/lib/x86_64-linux-gnu/libpthread.so.0+0x153bf)
      #4 0x7f4a3c7ff18a in raise (/lib/x86_64-linux-gnu/libc.so.6+0x4618a)
      #5 0x7f4a3c7de858 in abort (/lib/x86_64-linux-gnu/libc.so.6+0x25858)
      #6 0x7f4a3c7de728  (/lib/x86_64-linux-gnu/libc.so.6+0x25728)
      #7 0x7f4a3c7eff35 in __assert_fail (/lib/x86_64-linux-gnu/libc.so.6+0x36f35)
      #8 0x558f7588a913 in CScheduler::MockForward(std::chrono::duration<long, std::ratio<1l, 1l> >) scheduler.cpp:83:5
      #9 0x558f75b0e5b1 in mockscheduler()::$_7::operator()(RPCHelpMan const&, JSONRPCRequest const&) const rpc/misc.cpp:435:30
      #10 0x558f75b0e5b1 in std::_Function_handler<UniValue (RPCHelpMan const&, JSONRPCRequest const&), mockscheduler()::$_7>::_M_invoke(std::_Any_data const&, RPCHelpMan const&, JSONRPCRequest const&) /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:285:9
      #11 0x558f7587a141 in std::function<UniValue (RPCHelpMan const&, JSONRPCRequest const&)>::operator()(RPCHelpMan const&, JSONRPCRequest const&) const /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:688:14
      #12 0x558f7587a141 in RPCHelpMan::HandleRequest(JSONRPCRequest const&) const rpc/util.cpp:565:26
      #13 0x558f756c0086 in CRPCCommand::CRPCCommand(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, RPCHelpMan (*)())::'lambda'(JSONRPCRequest const&, UniValue&, bool)::operator()(JSONRPCRequest const&, UniValue&, bool) const ./rpc/server.h:110:91
      #14 0x558f756c0086 in std::_Function_handler<bool (JSONRPCRequest const&, UniValue&, bool), CRPCCommand::CRPCCommand(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, RPCHelpMan (*)())::'lambda'(JSONRPCRequest const&, UniValue&, bool)>::_M_invoke(std::_Any_data const&, JSONRPCRequest const&, UniValue&, bool&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:285:9
      #15 0x558f756b8592 in std::function<bool (JSONRPCRequest const&, UniValue&, bool)>::operator()(JSONRPCRequest const&, UniValue&, bool) const /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:688:14
      #16 0x558f756b8592 in ExecuteCommand(CRPCCommand const&, JSONRPCRequest const&, UniValue&, bool) rpc/server.cpp:480:20
      #17 0x558f756b8592 in ExecuteCommands(std::vector<CRPCCommand const*, std::allocator<CRPCCommand const*> > const&, JSONRPCRequest const&, UniValue&) rpc/server.cpp:444:13
      #18 0x558f756b8017 in CRPCTable::execute(JSONRPCRequest const&) const rpc/server.cpp:464:13
      #19 0x558f7552457a in (anonymous namespace)::RPCFuzzTestingSetup::CallRPC(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&) test/fuzz/rpc.cpp:50:25
      #20 0x558f7552457a in rpc_fuzz_target(Span<unsigned char const>) test/fuzz/rpc.cpp:354:28
      #21 0x558f7544cf0f in std::_Function_handler<void (Span<unsigned char const>), void (*)(Span<unsigned char const>)>::_M_invoke(std::_Any_data const&, Span<unsigned char const>&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:300:2
      #22 0x558f75c05197 in std::function<void (Span<unsigned char const>)>::operator()(Span<unsigned char const>) const /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/std_function.h:688:14
      #23 0x558f75c05197 in LLVMFuzzerTestOneInput test/fuzz/fuzz.cpp:74:5
      #24 0x558f753d8073 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) fuzzer.o
      #25 0x558f753c1f72 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) fuzzer.o
      #26 0x558f753c7d6a in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) fuzzer.o
      #27 0x558f753f3a92 in main (/root/fuzz_dir/scratch/fuzz_gen/code/src/test/fuzz/fuzz+0x5a8a92)
      #28 0x7f4a3c7e00b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
      #29 0x558f7539cc9d in _start (/root/fuzz_dir/scratch/fuzz_gen/code/src/test/fuzz/fuzz+0x551c9d)

ACKs for top commit:
  practicalswift:
    cr ACK fa2e614

Tree-SHA512: cfa120265261f0ad019b46c426b915c1c007806b37aecb27016ce780a0ddea5e6fc9b09065fd40684b11183dcd3bf543558d7a655e604695021653540266baf7