fix flaky batch timeout test

[aniketmaurya]

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

What does this PR do?

Fixes # (issue).

Fixes flaky batch timeout test. Before hitting the /predict endpoint it first checks if the server has actually started.

PR review

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79%. Comparing base (d096b80) to head (263d4d4).

Additional details and impacted files

@@         Coverage Diff         @@
##           main   #200   +/-   ##
===================================
  Coverage    79%    79%           
===================================
  Files        13     13           
  Lines      1040   1040           
===================================
  Hits        824    824           
  Misses      216    216           

[aniketmaurya]

@awaelchli could you also review it please?