Medium: IPaddr2 findif: accept dotted quad netmask

Accept, and noisily, but implicitly, convert a "cidr_netmask" parameter
that is specified as dotted quad.
Some people still do that, despite the name of the parameter.

And some previous versions of the IPaddr2 resource agent, or probably
rather the then used findif binary, accepted and converted it.
Merge pull request #516 from lge/rcf-findif-accept-dotted-quad-convert-to-cidr

Medium: IPaddr2 findif: accept dotted quad netmask