Put '/etc/HOSTNAME' into constant
Turned '/etc/HOSTNAME' -> '/etc/hostname'. bnc#858908

Purpose is to be cross platform compatible
Fixed testsuite
DNS module: cleanup
Updated testsuite
Small deduplication of DNS code
save_network: cleanup
Create symlink /etc/HOSTNAME to avoid backward compatibility issues.
Updated changelog
Merge pull request #208 from mchf/bnc858908-etc-hostname

Replaced /etc/HOSTNAME using cross platform /etc/hostname