cephadm: retry cleaning old cgroups when it fails

cephadm: retry cleaning old cgroups when it fails

It is possible that when attempting to redeploy a daemon
the shutdown of the daemon from cephadm running `systemctl stop`
may not have completed and we'll be unable to finish
cleaning the old cgroup. In these cases, moving on
immediately to try to start the systemd unit tends to
result in it failing to start. This patch adds a retry
to cleaning the old cgroups that should hopefully
avoid the race condition and daemons failing to start
because of it

Signed-off-by: Adam King <adking@redhat.com>