Fix environment checking for Pinot

[mik-laj]

In some cases, the validation of the environment may fail and end with the message below.

  /opt/airflow/scripts/in_container/check_environment.sh: line 41: -H 'accept: text/plain' | grep OK: syntax error: invalid arithmetic operator (error token is "'accept: text/plain' | grep OK")
  Presto (Broker API): .-----------------------------------------------------------------------------------------------

Unfortunately, Bash is not very obvious when it comes to multi-line text, and there is no type validation, so problems like this can happen.

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[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest master at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.