mon/OSDMonitor: warn when cache pools do not have hit_sets configured

Give users a clue when cache pools are enabled but the hit_set is not
configured.  Note that technically this will work, but not well, so for
now let's just steer them away.

Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 383536a2ef2506c5591b25c0fd61dc8c181fdab9)

NOTE: removed readforward state for backport
osd: prevent old clients from using tiered pools

If the client is old and doesn't understand tiering, don't let them use a
tiered pool.  Reply with EOPNOTSUPP.

Fixes: #8714
Backport: firefly
Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 0190df53056834f219e33ada2af3a79e8c4dfb77)