Convert interface names to underscores for facts

Convert interface names to underscores for facts

If a deployer uses an interface name with a dash/hyphen in it, such
as 'br-storage' for the monitor_interface group_var, the ceph.conf.j2
template fails to find the right facts. It looks for
'ansible_br-storage' but only 'ansible_br_storage' exists.

This patch converts the interface name to underscores when the
template does the fact lookup.

(cherry picked from commit 5676fa23b169e0ca3af7d4f9b804bbe90d1cccc6)
Signed-off-by: Sébastien Han <seb@redhat.com>