MQTT: remove standalone MQTT clien generator code.
Code was inherited from OPC-UA extension, but not properly maintained.
<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema" URI_location="LOCAL://">
<TargetType>
<Linux CFLAGS="-DBEREMIZ_TEST_CYCLES=1000"/>
</TargetType>
</BeremizRoot>