(Common response to all the comments about utInit and utExit)

I added two tests to mongoUpdateContext_test.cpp following the same style of the existing test in that file, which are not currently using the utInit / utExit functions.

However, given that this PR "touches" this file, I think it a good idea to use it for all the 45 TEST() it includes. In this way we are a step closer to our final goal of have 100% of TEST() using utInit / utExit functions :)