mon: add crush ruleset name to osd pool create

mon: add crush ruleset name to osd pool create

The ruleset to be used for the new erasure coded pool was expected in
the properties, under the name crush_ruleset. It does not belong to the
erasure code profile and needs to be added to the prototype explicitly.

The crush ruleset name is added to the prototype of the prepare_new_pool
and prepare_pool_crush_ruleset methods.

Signed-off-by: Loic Dachary <loic@dachary.org>