dax: ipacl: Allow to comment entries out

It may be useful to comment an entry out temporarily rather than simply
removing it.

Prefixing an entry with a '#' will cause that entry to be skipped over
for checking. e.g

    192.168.1.0/24
    #192.168.2.0/24
    192.168.100.100

will cause the second entry to be skipped.

Signed-off-by: Andrew Clayton <andrew@dnsandmx.com>