Fix(test-keys): usage: optional parameters

bin/test-keys

@@ -45,7 +45,7 @@ function teardown() {
 }
 
 function usage() {
-  echo "usage: $BASENAME <pool> <candidate> <port> <wait>"
+  echo "usage: $BASENAME <pool> <candidate> [port] [wait]"
   echo ""
   echo "Test an Onion Service keypair candidate mined in a pool"
   echo ""