Description of problem:

During host install, getCaps reports dhcpv6=true although it is set to no in the ifcfg of the iface on top of which vdsm is about to create ovirtmgmt bridge.

Version-Release number of selected component (if applicable):


How reproducible:
100%

Steps to Reproduce:
1. in ifcfg-eth0 set IPV6_AUTOCONF=yes, DHCPV6C=no
2. ifdown eth0 && ifup eth0
3. vdsm-client Host getCapabilities | grep eth0

Actual results:
{
     ...
             "eth0": {
            "ipv6autoconf": true, 
            "dhcpv6": true
     ...
}

Expected results:
{
     ...
             "eth0": {
            "ipv6autoconf": true, 
            "dhcpv6": false
     ...
}

Additional info:
CentOS Linux release 7.4.1708 (Core)
vdsm-4.30.0-166.git9fe9abd.el7.centos.x86_64
NetworkManager-1.8.0-11.el7_4.x86_64