OSDMap: respect default replicated ruleset config opt in build_simple()

OSDMap: respect default replicated ruleset config opt in build_simple()

Use id provided by osd_pool_default_crush_{replicated_ruleset,rule}
config options when creating a simple replicated ruleset for an initial
osdmap instead of always making it ruleset 0.  Not doing so may leave
default created pools (currently "rbd") in a broken state with their
crush_ruleset pointing to a non-existent ruleset.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>