make php tests run under python3 again
make php tests run under python3 again

Summary:
The test classes were only discoverable on python 2.
Rename our main test method to make it work on both versions.

Reviewed By: zertosh

Differential Revision: D5681853

fbshipit-source-id: 03cb4afcf0fb409c4f9d0a17db02298428ed756a

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