handle interrupted test suite runs

[comboy]

There's need to be some mechanism to handle test's suites that are left in the running state. We cannot prevent this from happening completely (ruby may segfault during test suite run, we could use transaction maybe, but then live status on the page wouldn't work), so we need to handle it somehow.

• it could be job cleaning up test suite runs that are running above X time
• if workers would register, then we can check what worker locked the instance and see if it is alive