mon: allow mgr to tell mon.foo smart

mon: allow mgr to tell mon.foo smart

The mgr profile needs to do a tell command to the mon, which was restricted
to *only* allow_all (*) caps.  Additionally allow whitelisted commands,
and whitelist 'smart'.  This is somewhat imprecise since it conflates
tell vs cli commands in the MonCap, but since those don't overlap it should
be fine.

Signed-off-by: Sage Weil <sage@redhat.com>