Handle case of not setting options; do not return options we don't set

On OSX machines I have tested:

lib/puppet/provider/printer/cups.rb: blows up about calling include? on nil when you don't set options.
AND
Continues to try and set every possible option listed by lpoptions -l instead of just the options you pass as a hash.

This fixes both of those by putting back some code that was removed in the past.
I copied it, more or less, from the 1.3.0 branch.