Fixed QMQTT::Message unit test.
Fixed QMQTT::Message unit test.

The test was broken in commit 420db41c0898cac8331d1bac2aee1c60201bfecd
because it introduced a 2bit bitfield to store the QoS. The unit
tests on QMQTT::Message assumed it was possible to store a QoS of 5,
which does not fit in the bitfield.

KonstantinRitt/qmqtt,KonstantinRitt/qmqtt,KonstantinRitt/qmqtt,KonstantinRitt/qmqtt