Check ceph_health_raw.stdout value as string during mon bootstrap

Check ceph_health_raw.stdout value as string during mon bootstrap

According to rdo testing https://review.rdoproject.org/r/#/c/18721
a check on the output of the ceph_health value is added to
allow the playbook to make several attempts (according to the
retry/delay variables) when waiting the cluster quorum or
when the container bootstrap is not ended.
It avoids the failure of the command execution when it doesn't
receive a valid json object to decode (because cluster is too
slow to boostrap compared to ceph-ansible task execution).

Signed-off-by: fpantano <fpantano@redhat.com>
(cherry picked from commit afbb90e4acb6e0bacddf52bb512bef74b013fa68)