qmlprofiler: Clean up recording state mess

qmlprofiler: Clean up recording state mess

The recording state is a global property of the profiler client, it has
to match the application's recording status as well as possible, and
the user can set an initial target value with a command line parameter.

This way we don't get strange error messages when the application quits
by itself and properly sends all the data before.

Task-number: QTBUG-43066
Change-Id: Id93aa7fb940f870c8f16cea8427c38aab450f864
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>