filestore-to-bluestore: fix osd_auto_discovery

filestore-to-bluestore: fix osd_auto_discovery

When osd_auto_discovery is set then we need to refresh the
ansible_devices fact between after the filestore OSD purge
otherwise the devices fact won't be populated.
Also remove the gpt header on ceph_disk_osds_devices because
the devices is empty at this point for osd_auto_discovery.
Adding the bool filter when needed.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1729267
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>