Fix for BUG#22074: mysql-test-run.pl abort test run if it fails

to start instance manager.

The problem was that if IM failed to start, test suite aborts.

The fix is to mark current test as failed, and continue running
test suite.

The fix affects only test suite.

mysql-test/mysql-test-run.pl

@@ -2114,7 +2114,10 @@ sub run_testcase ($) {
 
       unless ( mtr_im_start($instance_manager, $tinfo->{im_opts}) )
       {
-        mtr_error("Failed to start Instance Manager.")
+        report_failure_and_restart($tinfo);
+        mtr_report("Failed to start Instance Manager. " .
+                   "The test '$tname' is marked as failed.");
+        return;
       }
     }