worker: fix missed break on successful waitpid()

Follow-up for 5069a8a40b1b.

mercurial/worker.py

@@ -102,6 +102,7 b' def _posixworker(ui, func, staticargs, a'
             while True:
                 try:
                     p, st = os.waitpid(pid, (0 if blocking else os.WNOHANG))
+                    break
                 except OSError as e:
                     if e.errno == errno.EINTR:
                         continue