issue #406: ensure is_path_dead() socket is finalized.

mitogen/unix.py

@@ -48,11 +48,14 @@ from mitogen.core import LOG
 
 def is_path_dead(path):
     s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    try:
         try:
             s.connect(path)
         except socket.error:
             e = sys.exc_info()[1]
             return e.args[0] in (errno.ECONNREFUSED, errno.ENOENT)
+    finally:
+        s.close()
     return False