all: Actually honor public DNS set in IDF

all: Actually honor public DNS set in IDF

We currently do not configure linux:network:resolv:dns via reclass
pillar data, so we don't actually enforce the public DNS set in
the IDF file, but instead leave it to the OS to figure it out, which
most of the time works fine, but it's not completely reliable.

Change that behavior to instead enforce it via linux.network.resolv
state across all cluster nodes.

Change-Id: I4f82315a473fcbdc8573380cfcac1e30b44c3dd4
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>