Using
createPacketCollector(filter);
sendPacket(packet);
was error prone, i.e. the PacketCollector could leak if sendPacket()
would throw an exception and the user forgot to call
PacketCollector.cancel(). For cases where
createPacketCollectorAndSend(IQ) is not sufficient (because we don't
send IQs), createPacketCollectorAndSend(PacketFilter, Packet) is now
used, which does take care that the PacketCollector does not leak if
sendPacket() throws an Exception.