Fixed a race condition in loop_invariance_extern_calls test
Fixed a race condition in loop_invariance_extern_calls test


Former-commit-id: 76aaad1b76f714747f533459ef790cc17d51b1f4
Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide