ceph_manager: update ec_pool creation parameters

As of https://github.com/ceph/ceph/pull/1477 the erasure code parameters
are controled via the osd erasure-code-profile set command instead of
being inlined and duplicated in the crush ruleset creation and the pool
creation. There is no need to create the crush ruleset, it is done
implicitly.

Signed-off-by: Loic Dachary <loic@dachary.org>