Fix qbluetoothsocket unit test

Task-number: QTBUG-22017
Change-Id: I876b8a052873d198e8991b7eab3ca70714eb0dcc
Reviewed-by: Nedim Hadzic <nedimhadzija@gmail.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Remove btclient

It is replaced by bttestui which runs on any platform and is
the official test tool for a variety of other tests too.

Task-number: QTBUG-22017
Change-Id: Ia675876375901a0f19d1820e2167729aa863bd34
Reviewed-by: Nedim Hadzic <nedimhadzija@gmail.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>