Upgrade mockRoom to implement EventEmitter like mxRoom does

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

test/matrix-to-test.js

@@ -57,6 +57,8 @@ function mockRoom(roomId, members, serverACL) {
                 }
             },
         },
+        on: () => undefined,
+        removeListener: () => undefined,
     };
 }