DNM: osd: disable omap if the pool is not replicated

If one of the operations in MOSDOp is CEPH_OSD_OP_OMAP* and the pool is
not replicated, return EINVAL.

http://tracker.ceph.com/issues/6895 fixes #6895

Signed-off-by: Loic Dachary <loic@dachary.org>