ceph_manager: wait for dump_ops_in_flight on osd revival

Wait for a command that implies a complete startup instead of
'version' (which does not).

Fixes: #5924
Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 5ec5e2c0e2e0cb4e25071999a05d9ac6294c3797)