Stub in_path? call in Rubocop specs

Specs were failing in Travis but not locally since we have Rubocop
installed locally.

Change-Id: Ib2f4910dd3d3731a98de55c9e2bacc42b9aba914
Reviewed-on: http://gerrit.causes.com/35877
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>