vttestserver should only pass a BindAddressGprc if one is passed in

[anirbanmu]

If none is passed in, it should pass nothing causing gRPC port to be bound to all interfaces (instead of just 127.0.0.1).

Fixes #17396

I verified the fix using the repro script detailed here.

Description

This is making the change suggested in #17396 (comment). When there is no gRPC bind address given, we should pass nothing to the vtcombo process, so that we bind to all network interfaces rather than just 127.0.0.1 as it was doing before.

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

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[mattlord]

Thanks, @anirbanmu ! ❤️

[mattlord]

@anirbanmu You'll need to sign your commit and force-push as described here: https://github.com/vitessio/vitess/pull/17457/checks?check_run_id=35077958638

[anirbanmu]

@anirbanmu You'll need to sign your commit and force-push as described here: https://github.com/vitessio/vitess/pull/17457/checks?check_run_id=35077958638

Thanks for the heads up! I think I've done it just now.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.65%. Comparing base (b8b0383) to head (ee5b634).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17457      +/-   ##
==========================================
- Coverage   67.65%   67.65%   -0.01%     
==========================================
  Files        1584     1584              
  Lines      254360   254360              
==========================================
- Hits       172097   172079      -18     
- Misses      82263    82281      +18     

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