Ceph: be more resilient to malfunctioning OSDs

There's currently an issue where a single malfunctioning OSD (or
multiple of them) can mark down all of the other OSDs. This is the
behavior previously described by yours truly on
http://tracker.ceph.com/issues/4552
and supposedly fixed in the next version (Cuttlefish).

However, we did have an outage because of this an hour ago, so it seems
at least prudent to increase the number of reporters for now. Set it to
14, i.e. the number of OSDs in a single box + 2, as to protect
ourselves from a malfunctioning or otherwise hung SCSI controller as
well, as was 4552's case.

Change-Id: Ia7cd6618e0bf9983ab7c22b53de7eb9c0e35c998