This adds a new check to make sure msgr2 is enabled if it is
supported by all of the mons. When mon quorum is lost the
mons revert to the v1 protocol, which results in a Ceph
warning state if v2 is supported by all of the available
mons.
Change-Id: Ib85243d38f122c1993aba945b7ae943eed262dbf