mon/OSDMonitor: encode canonical full osdmap based on osdmap flags

mon/OSDMonitor: encode canonical full osdmap based on osdmap flags

If the JEWEL or KRAKEN flags aren't set, encode the full map without
those features.  This ensure that older OSDs in the cluster will be able
to correctly encode the full map with a matching CRC.  At least, that is
true as long as the encoding changes are guarded by those feature bits.
That appears to be true currently, and we plan to ensure that it is true
in the future as well.

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