bz 1059417,1056892 -- Handle interface names containing "."

https://bugzilla.redhat.com/show_bug.cgi?id=1056892
https://bugzilla.redhat.com/show_bug.cgi?id=1059417

This fixes problems with VLAN interfaces in astapor by calling
regsubst() to replace "." with "_" in interface names when looking up
ipaddress_* facts.