erasure-code: preload the default plugins in the mon (firefly)

The commit 164f1a1959a863848319585fa752250c7b261381 preloads the
jerasure plugin in the OSD. They must also be preloaded in the mon for
the same reasons.

http://tracker.ceph.com/issues/9273 Fixes: #9273

Signed-off-by: Loic Dachary <loic-201408@dachary.org>