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>
Could you add a test modeled after **function TEST_erasure_code_profile_default_pending() {** that demonstrates https://github.com/ceph/ceph/pull/2138/files#diff-0a5db46a44ae9900e226289a810f10e8R3322 is reached when expected ? The monitor keep changes in **pending** for a short while and then propose the changes to the other monitors. When that happens, you return EAGAIN and expect the command to be evaluated after the ruleset moved from **pending** to the real crush map. That's what you coded and it looks good. The goal of the test is to prove that it does and protect this rare condition from future regressions. Please let me know if you need explanations on how **function TEST_erasure_code_profile_default_pending() {** works.