If no drones are running, but drone_registry contains non-existent drones, Tardis crashes

[olifre]

Stacktrace:

root: 2019-09-28 12:15:28 Destroying VM with ID 7132
cobald.runtime.runner.asyncio: 2019-09-28 12:15:28 runner aborted: <cobald.daemon.runners.asyncio_runner.AsyncioRunner object at 0x7f746d6e70b8>
Traceback (most recent call last):
  File "/opt/cobald/lib64/python3.6/site-packages/tardis/adapters/sites/htcondor.py", line 149, in handle_exceptions
    yield
  File "/opt/cobald/lib64/python3.6/site-packages/tardis/agents/siteagent.py", line 45, in terminate_resource
    return await self._site_adapter.terminate_resource(resource_attributes)
  File "/opt/cobald/lib64/python3.6/site-packages/tardis/adapters/sites/htcondor.py", line 138, in terminate_resource
    response = AttributeDict(pattern.search(response.stdout).groupdict())
AttributeError: 'NoneType' object has no attribute 'groupdict'

The cause should be that:

tardis/tardis/adapters/sites/htcondor.py

Lines 91 to 93 in e771903

	response = await self._executor.run_command("condor_submit", stdin_input=submit_jdl)
	pattern = re.compile(r"^.*?(?P<Jobs>\d+).*?(?P<ClusterId>\d+).$", flags=re.MULTILINE)
	response = AttributeDict(pattern.search(response.stdout).groupdict())

does not check if pattern.search is a NoneType before using it.

CC @wiene

[giffels]

Thanks for reporting. Same as #82