Update the WMI Script handling Hyper-V friendly port names

This patch ensures that the friendly port name has no more than 16 characters
and also if it is not in use.

The method which checks the WMI jobs has been updated in order to provide
relevant error codes/descriptions.

Methods retrieving the according VM and VM network adapter mapped to an OVS
port have been added as well. They are called:
Get-VMNetworkAdapterByOVSPort
Get-VMByOVSPort

Example of usage:
 2 import-module .\OVS.psm1
 3 $vnic = Get-VMNetworkAdapter test_2_1
 4 $vnic[0] | Set-VMNetworkAdapterOVSPort -OVSPortName ovs-port-1
 5 $vnic[1] | Set-VMNetworkAdapterOVSPort -OVSPortName ovs-port-1
 6 $vnic[0] | Set-VMNetworkAdapterOVSPort -OVSPortName ovs-port-2
 7 $vnic[1] | Set-VMNetworkAdapterOVSPort -OVSPortName ovs-port-1
 8 Get-VMNetworkAdapterByOVSPort ovs-port-1
 9 Get-VMByOVSPort ovs-port-2

Signed-off-by: Lucian Petrut <lpetrut@cloudbasesolutions.com>
Tested-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>