Added ability to specify mac in deployVirtualMachine and
addNicToVirtualMachine api endpoints.
Validates mac address to be in the form of:
aa:bb:cc:dd:ee:ff , aa-bb-cc-dd-ee-ff , or aa.bb.cc.dd.ee.ff.
Ensures that mac address is a Unicast mac.
Ensures that the mac address is not already allocated for the
specified network.