ceph-facts: use last ipv6 address for mon/rgw

ceph-facts: use last ipv6 address for mon/rgw

When using monitor_address_block or radosgw_address_block variables
to configure the mon/rgw address we're getting the first ip address
from the ansible facts present in that cidr.
When there's VIP on that network the first filter could return the
wrong value.
This seems to affect only IPv6 setup because the VIP addresses are
added to the ansible facts at the beginning of the list. This is the
opposite (at the end) when using IPv4.
This causes the mon/rgw processes to bind on the VIP address.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1680155
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>