Fix return value in shm_test for opensource
Fix return value in shm_test for opensource

Some machines return 128 + signal for failures. Accept that
as a valid result.

PiperOrigin-RevId: 327326113

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor