[IntelliJ]Can't find AU warning label when user provision a new Spark on ADL cluster.

[v-jiche]

Build:
azure-toolkit-for-intellij-2018.2.develop.824.10-29-2018

Repro Steps:

1. Open Provision Spark Cluster.
2. Change the Number of Containers until required AU is greater than available AU.
3. Then tab it.

Result:
Can't find AU warning label.

[t-rufang]

[v-jiche]

Verified, Fixed.
Build: azure-toolkit-for-intellij-2018.3.develop.965.01-16-2019