Don't try install dnsmasq for sledgehammer image

Sledgehammer for SLES was updated and it is build with dnsmasq package. We don't want install it once again when node is booted with sledgehammer image.
127.0.0.1 is added here: https://github.com/crowbar/barclamp-dns/pull/113/files#diff-c44a26f153e99750b70d4f1339a33c54R60