Added support for RedHat in ceph::mon

Support for the RedHat family in ceph::mon.

Changes mostly affect the tests, as check commands
need to be adapted depending on the os(family).

The CephOS 6.4 box currently used in CI has a firewall
preinstalled. Therefore multi-node tests need to flush the firewall.

Change-Id: I51150c1e3316bdab20c4458e79c4aeeb15fe4bd2
Closes-Bug: #1264916
Refactored mon CI test to use before/after

Change-Id: I86aba01719052a72ff4611fd5846c590ebae8d5c
Merge branch 'wip/bug/1264916' of github.com:ninech/puppet-ceph into wip/bug/1264916

Conflicts:
	spec/system/ceph_mon_spec.rb

Change-Id: Ib95e636304acef50c55a335d98658bb1f2c53c97