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Let the service controller retry when presistUpdate returns a conflict error

**What this PR does / why we need it**:
If a load balancer is changed while provisioning, it will fall into an error state and will not self-recover.
This PR picks up the conflict error and let serviceController retry in order to get the load balancer out of error state.

**Special notes for your reviewer**:
/assign @MrHohn @rramkumar1 

**Release note**:

```release-note
Let service controller retry creating load balancer when persistUpdate failed due to conflict.
```