Only check for orphaned tests in projects explicitly being built (#2518).

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@22046 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2560 Potential fix, and now passing test. Also tidying.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@22047 b5f69653-2bf5-0310-8201-b0dafb8e1405