Add another test that checks priority scheduling in the case of

[pintos-anon] / src / tests / threads / Rubric.priority

Functionality of priority scheduler:
3       priority-preempt
3       priority-donate-one
3       priority-donate-multiple
3       priority-donate-multiple2
3       priority-donate-nest
3       priority-donate-sema
3       priority-change

3       priority-fifo
3       priority-sema
3       priority-condvar