plug_vif raise NotImplementedError instead of pass

The Hyper-V, VMware, Docker and PowerVM drivers raise
NotImplementedError from the plug_vifs and unplug_vifs
methods rather than pass.
The compute manager handles the NotImplementedError
case when initializing the host.

Fixed bug 1218593

(cherry picked from commit 6ef9262a6aa39b2da8023067386b832a35ecc45c)

Conflicts:

	nova/tests/virt/hyperv/test_hypervapi.py
	nova/tests/virt/vmwareapi/test_vmwareapi.py
Change-Id: Id17a1f691f46816eadfe257d9ac0cc46502318ef
VMware: fix exception when using multiple compute nodes

When there is more than one compute node running and one of the
nodes restarts it terminates on an exception that the resource is
not found.

The cause of the issue is that a vif plug was being attempted for
a resource that did not exist. The vif plug should have raised an
"NotImplemented" exception.

Change-Id: I5a3f1cc73a981173b6c2fa493de3aad10a7e97fd
Closes-bug: #1272286
(cherry picked from commit d46f4a5b6d17f20a9c1de9367af11c9f3e7a7ef0)
Merge "plug_vif raise NotImplementedError instead of pass" into stable/havana
Merge "VMware: fix exception when using multiple compute nodes" into stable/havana