pd-ctl should return non-zero exit code on error

## Enhancement Task
In some automated scripts, it is hard to tell if a command succeeds because pd-ctl returns 0 on error.

For example:
```
[root@tidb-cluster-tikv-0 /]# /pd-ctl -u "$PD_ADDRESS" store delete addr ""
address not found: 
[root@tidb-cluster-tikv-0 /]# echo $?
0
```