allow parallel test runs to not destory eachother

Summary: I'm digging into t4686420 and I found that running many instances of the runner puke all over eachother. http://php.net/manual/en/function.msg-get-queue.php makes it look like you can just any integer here you want as long as it is the same one.

Reviewed By: @swtaarrs

Differential Revision: D1474408