rados.py: fix create_pool()

Call rados_pool_create_with_all() only if auid and crush_rule
are set properly. In case only crush_rule is set call
rados_pool_create_with_crush_rule() on librados, not the other
way around.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
(cherry picked from commit 94a1f25e7230a700f06a2699c9c2b99ec1bf7144)
Merge pull request #210 from dalgaaf/wip-da-bobtail-pybind

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>