vmcheck/multitest: Print when we're waiting

To help debug.

Closes: #1676
Approved by: cgwalters

tests/vmcheck/multitest.py

@@ -105,6 +105,7 @@ class Host:
     def flush(self):
         if not self._p:
             return 0
+        print("WAITING: {} (pid={})".format(self.test, self._p.pid))
         rc = self._p.wait()
         endtime = time.time()