mon: elevate priority of many perf counters

mon: elevate priority of many perf counters

We can be quite liberal here, because mons are
small in number.  However, we don't want to expose
KV database counters at this database from OSDs, so
use the prio_adjust mechanism for that.

Signed-off-by: John Spray <john.spray@redhat.com>
(cherry picked from commit ac8320f23dd4c00eb80da0d9837c29744e38bd57)