Automatic merge from submit-queue (batch tested with PRs 50091, 50231, 50238, 50236, 50243)

Modify e2e.go to arbitrarily pick one of zones we have nodes in for multizone tests.

**What this PR does / why we need it**:
When e2e runs in multizone configuration, zone config property can be empty.
This PR, in that case, overrides an empty value with arbitrarily chosen zone that we have nodes in.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:
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