Fix test MAC addresses to be valid

MAC addresses should have 6 octets - 'ff:ff:ff:ff:ff:ff'.

Change-Id: I9c2457d978ccce15549d3258961093a130375bff
Closes-bug: #1302282
(cherry picked from commit 5f042a64308cb00698b454da09b4a87f2ac3fafd)
Merge "Fix test MAC addresses to be valid" into milestone-proposed