when running tests in sandcastle, don't exit(1)
when running tests in sandcastle, don't exit(1)

Summary:
Our infra is categorizing the test run as flaky because
of the exit status for just one test.  Leave it to parse the test
output to correctly report on a deal with this.

Reviewed By: simpkins

Differential Revision: D5295289

fbshipit-source-id: 9cfa962c36c74f974c0503de2d84110406482d4e

wez/watchman,facebook/watchman,nodakai/watchman,kwlzn/watchman,facebook/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman,wez/watchman,kwlzn/watchman,kwlzn/watchman,wez/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,wez/watchman,wez/watchman,nodakai/watchman,nodakai/watchman,kwlzn/watchman,kwlzn/watchman,nodakai/watchman,kwlzn/watchman,wez/watchman,wez/watchman,facebook/watchman,nodakai/watchman,wez/watchman,facebook/watchman,kwlzn/watchman,nodakai/watchman,wez/watchman,facebook/watchman