Drop sudo requirement from a unit test

I noticed while working on some other stuff that a unit test was
prompting me for my sudo password.  I narrowed it down to the
offending test case and fixed it by mocking out the execute util, as
is done in several other places in these tests.

Change-Id: I93c6cdb8a26d3be5df5386091dc70a240ab7c190
Closes-bug: #1396276
Merge "Drop sudo requirement from a unit test"