Use lockutils module for tox functional env

A previous change (I4d6076e5f7586a11ea5381f18774d4bab57b0081) added
lockutils to only the dsvm-functional tox env.  It also needs to be
added to the functional tox env.

Change-Id: I3a799692b2162b738a2b080e08602b403c171e4f
Closes-Bug: 1332380
Merge "Use lockutils module for tox functional env"