mon: compact full epochs also

by compacting the ${prefix}.${start}..${prefix}..${end} does not
necessary compact the range of ${prefix}."full_"${start}..
${prefix}."full_"${end}. so when more and more epochs get trimmed
with out a full range compaction, the size of monitor store could
be very large.

Fixes: ceph#14537
Signed-off-by: Kefu Chai <kchai@redhat.com>

src/mon/PaxosService.cc

@@ -388,6 +388,9 @@ void PaxosService::trim(MonitorDBStore::TransactionRef t,
   if (g_conf->mon_compact_on_trim) {
     dout(20) << " compacting prefix " << get_service_name() << dendl;
     t->compact_range(get_service_name(), stringify(from - 1), stringify(to));
+    t->compact_range(get_service_name(),
+		     mon->store->combine_strings(full_prefix_name, from - 1),
+		     mon->store->combine_strings(full_prefix_name, to));
   }
 }