Provide the ability to provide monitor_address instead of an interface

Provide the ability to provide monitor_address instead of an interface

This would allow users who don't know what interface to provide to
give an IP address to use for the monitor instead.

Note: the includes are needed in ceph.conf.j2 because without them
jinja2 can not properly evaluate the template and will complain about a
missing 'ansible_interface' variable. The includes allow the template to
be evaluated correctly and then the correct include will be used during
render time.

Signed-off-by: Andrew Schoen <aschoen@redhat.com>