Fix bug in source file test.

When looking for a source file, it was assumed that the current working
directory did not contain the character '.'. If the working directory did
contain a '.', this test would fail.
Merge remote-tracking branch 'upstream/develop' into lc_fix
Merge branch 'lc_fix' of github.com:nelsonag/openmc into lc_fix
Updated results_true.dat to  correspond with the updated test.