ceph_manager::wait_for_clean: reset timeout if we make progress

Fixes: #7748
Signed-off-by: Samuel Just <sam.just@inktank.com>
ceph_manager: default to 16 initial pgs per pool

1 is really too few for anything to happen at a
reasonable rate.

Signed-off-by: Samuel Just <sam.just@inktank.com>