Imrove stability of grok regexes

After the fix, msg rate increased x20 (20->350+)
Do not use back dns resolve!
TODO fix broken multiline for openstack logs

Change-Id: I6729089e6cb007e482e9a8656710a033c199abbd
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>