Fix neutron jobs for tempest on stable branches

Neutron full job is now voting for juno, the smoke one can be
dropped as it is redundant.

Icehouse full job is non-voting for icehouse, so it should be
dropped as we do not run non-voting jobs on stable.

Change-Id: I63ceb672f9d2643695e0fcf27e6df77f91c4db51
Merge "Fix neutron jobs for tempest on stable branches"