Fix extension description and remove unused exception

Change-Id: Id0a40a8decb46e306256196c7fc79d687d4f8075
Closes-Bug: #1267841
Remove extra whitespace

Remove an extra whitespace in the __str__ routine for the
VifPort class

Change-Id: Ie4a7d011af1697d2e6f523dfe00244aaa42d5127
Merge "Remove extra whitespace"
Merge "Fix extension description and remove unused exception"