Bug 1516861

Created attachment 1358205 [details]
Logs

Description of problem:
[DNS] - User defined dns severs should be absolute.

If host was added with 3 name servers in the resolv.conf and the user set 1 new dns configuration via the engine, the resolv.conf update only the first name server in the resov.conf and keeping the 2 others, but this is not good and not absolute, this will keep the host as out-of-sync for ever.
Engine will complain that the host has 3 name servers, but DC only one.
If user choose to set 1 name server, then all other name servers in the conf must be overridden.

Version-Release number of selected component (if applicable):
4.2.0-0.0.master.20171121184703.git173fe83.el7.centos

How reproducible:
100%

Steps to Reproduce:
1. Add host with 3 name servers, the management network should be with static bootproto, because all dhcp scenarios + DNS feature will end up as out-of-sync almost 100% of the time - See BZ 1451261
2. Go to the management network in the ui and set new 1 name servers in the DNS configuration checkbox in the edit network dialog.
3. Approve operation

Actual results:
resolv.conf was updated with the new name server, the first name server in the conf was overridden, but the 2 other name servers remain, which caused the engine to report that management network is out-of-sync, but he also report that the change was successfully applied(because managed to apply the change, but not absolutely).

Expected results:
User defined dns severs should be absolute, which means to override all name servers in the resolv.conf except the specified by the user and make the host in sync.