mon/OSDMonitor : Use user provided ruleset for replicated pool

When creating a replicated pool, currently ceph ignore the ruleset
name provided by user but use a global default ruleset.

This patch fix this bug, so the rulset specified by
 ceph osd pool create <pg_num> <pgp_num> replicated <my_ruleset_name>
can be properly set.

Signed-off-by: Xiaoxi Chen <xiaoxi.chen@intel.com>
the default is the value of the **osd_pool_default_crush_replicated_ruleset** configuration variable