Ceph: adjust a few OSD settings

Revert to the default values of some very large timeouts (op thread &
recovery thread, set to 7200 from 30) and lower min pg log entries to
300 from 3000 by sjust's advice for the slow peering issue.

Change-Id: Icbf9dcca649fd3f3cdeef711f9672d3dd0e31815