(RE-3310) Update mock task to corrrectly parse mock name

When the PE version was removed from some mocks, it broke some
assumptions in the mock rake task. This commit addresses that by using a
regex capture instead of splitting, to allow for the PE version to be
optional.
Merge pull request #356 from haus/ticket/master/re-3310-update-mock-parsing

(RE-3310) Update mock task to corrrectly parse mock name