Automatic merge from submit-queue (batch tested with PRs 62748, 60536, 62300, 62661, 62731). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
[GCE] Parallelize GCE loadbalancer tests
**What this PR does / why we need it**:
- Encapsulate IP counter in Mocks. Previously, ipCounter was a global int modified by multiple tests.
- Use mock-provided Lock before modifying resources.
- Parallelize loadbalancer tests.
```release-note
NONE
```
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