nwfilterxml2firewalldata: Use internal wrapping to wrap output files

nwfilterxml2firewalldata: Use internal wrapping to wrap output files

As with previous commits use virCommandSetDryRun to invoke
virCommandToString so that it returns pre-wrapped string.

Since virCommand is better aware of where the arguments terminate we can
see an improvement where comments are no longer line-wrapped.

The changes to the 'commonRules' strings were done with the following
regex:

 s/ -/ \\\\\\n-/

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>