orly/server/tetris_manager.test fails intermittently. Disable it.

Sample failure:

Running test: orly/server/tetris_manager.test
[orly/server/tetris_manager.test.cc, 390](int)global_pov->Sum() == (int)expected_sum; 69 == 72; fail
end Typical; fail
passed 0, failed 1
Merge pull request #77 from cmaloney/tetris_manager_nondeterministic

orly/server/tetris_manager.test fails intermittently. Disable it.