PROG Second attempt to fix the race condition in findimageoverlaps, added more...

PROG Second attempt to fix the race condition in findimageoverlaps, added more locks around p_lonLatOverlaps manipulation. References #2199.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@7125 41f8697f-d340-4b68-9986-7bafba869bb8