Describe the bug
Keptn installation fails on AKS cluster with the following error:
az failed to describe the cluster for retrieving the property.

To Reproduce
Steps to reproduce the behavior:

1. Run keptn install --platform=aks
2. Enter information
3. See error

Expected behavior
Installation should continue

Environment
Kubernetes version 1.12.8

Additional context
The installer fails with:

Deploying keptn installer pod...
Installer pod deployed successfully.
Getting logs of pod installer-7494494f54-fkkqf
Starting installation of keptn
CLUSTER_IPV4_CIDR is not set, retrieve it using az.
az failed to describe the cluster for retrieving the property.
Error: keptn installation was unsuccessful

az is installed locally and working fine. Taking a look at the installer container logs, it looks like the installer is trying to use az from the container though and can't find it:

##########
branch: master
repository: https://github.com/keptn/installer
commitlink: https://github.com/keptn/installer/commit/5fcdd6f2d826f5015d0b98815fb53b03340630c3
repolink: https://github.com/keptn/installer/tree/5fcdd6f2d826f5015d0b98815fb53b03340630c3
travisbuild: https://travis-ci.org/keptn/installer/jobs/551781339
timestamp: 20190628.1528
##########Install on AKS
[keptn|INFO] [2019-07-01 12:55:09] Starting installation of keptn
[keptn|DEBUG] [2019-07-01 12:55:09] CLUSTER_IPV4_CIDR is not set, retrieve it using az.
./aks/installOnAKS.sh: line 44: az: command not found
[keptn|ERROR] [2019-07-01 12:55:09] az failed to describe the cluster for retrieving the property.