mon: remove racy tests from osd-pool-create.sh

Use the admin socket to create the conditions by which a pool creation
is made to wait for the next paxos proposal because the required crush
ruleset is pending.

It replaces a fragile time sensitive workaround that could fail because
of race conditions. It also has the benefit of increase the speed of the
test because there is no need to wait for a long time just to accomodate
the slowest machines.

Signed-off-by: Loic Dachary <loic@dachary.org>