Enhance the DB connection check.
    
    This commit is based on one of the commits by Michal Schorm
    <mschorm@redhat.com>. Thanks!
    
    * https://src.fedoraproject.org/rpms/rubygem-mysql2/pull-request/13
      - [5/6] Testsuite fix - enhance the error handling of the loop that checks
        whether the DB server is alive
    * https://bugzilla.redhat.com/show_bug.cgi?id=2144488#c2
      - (3) While waiting for the DB server to come online
    
    In the previous logic, the DB connection logic didn't exit correctly with error
    when the last 10th try still fails. The new logic makes the logic fail
    properly, and prints the DB error log file. The printed log makes us debug
    easily.