mon/OSDMonitor: health warn if require_{jewel,kraken} flags aren't set

mon/OSDMonitor: health warn if require_{jewel,kraken} flags aren't set

We want to prompt users to set these flags as soon as their
upgrades complete.

Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 12e508313dbd5d1d38c76859cb7de2ce22404e12)

Conflicts:
   src/mon/OSDMonitor.cc: remove references to kraken

    if ((osdmap.get_up_osd_features() & CEPH_FEATURE_SERVER_KRAKEN) &&
	!osdmap.test_flag(CEPH_OSDMAP_REQUIRE_KRAKEN)) {
      string msg = "all OSDs are running kraken or later but the"
	" 'require_kraken_osds' osdmap flag is not set";
      summary.push_back(make_pair(HEALTH_WARN, msg));
      if (detail) {
	detail->push_back(make_pair(HEALTH_WARN, msg));
      }
    } else