Do not remove line from /etc/hosts if it contains two spaces. bnc#769081

Ported from SLE branch.
Updated testsuite for bnc#769081
Updated changelog.
YaPI syntax warning fixed. bnc#810539
Updated changelog
do not write network config files if not changed. fate#308978
Updated changelog.
Refactoring ported patch for fate#308978

Removed useless Convert (added during conversion from ycp).

Replaced temporary variables tmp1, tmp2 using one in DNS::Write.
Merge pull request #107 from mchf/bnc831833-regressions

Fixes ported from SLE branch