Increase the timeout for QPacketProtocol tests

Recent failures when testing a completely unrelated one-line commit
(https://codereview.qt-project.org/74584) suggest that the timeout is
actually too small.

Change-Id: I9c3fd0b09c6be2d42f92485c3c223fe88bb8328e
Reviewed-by: Michael Brasser <michael.brasser@live.com>