Improving test playback reliability with pqLineEdit.

pqLineEdit during playback of tests could end up not firing the
textChangedAndEditingFinished() signal which resulted in incorrect test
playback. Ensuring that the signal is explicitly fired by
pqLineEditEventPlayer when set_string event is played back.

Change-Id: I0977ed4819d7a0cfae9b6ce11f453d9ff31af8f8
Merge topic 'refactor_python_tracing_2' into next

4bbd36fe Improving test playback reliability with pqLineEdit.