Deja Gnu Unit Tests

1. These tests execute only when Slurm is built directly in the source
   directory, not when a separate build directory is used.
2. Ensure the "expect", "dejagnu" and "check" packages are installed.
3. From the top level source directory, execute "make check", which builds
   the executable files including various src/common/*.o files that will be
   unit tested.
3. Change working directory to "testsuite/slurm_unit".
4. Execute "make check" to execute the unit tests.
