qml: do not automatically show player view

Since addAndPlay() is not synchronous, showing the player does not represent the correct state.

This causes:

• Confusion. Nothing is played, but player view is being shown.
• Loading expensive background image of the current item (in case of audio files) before starting playing the new one.

Currently, the player view should automatically open when there is embedded video output. One might claim that it is good idea to prepare the player view before starting playing, but this argument can be refuted because currently player is opened after a play request is made.