ToneGenerator: fix use of STREAM_VOICE_CALL

ToneGenerator is only used for signalling, never for voice.
In order to use proper audio attributes usage and content type, convert
requests to play on stream VOICE_CALL to stream DTMF.
This will produce consistent routing and volume behavior when apps use
DTMF or VOICE_CALL streams.
Also use audio attributes when creating the AudioTrack

Test: CTS for ToneGenerator, voice and VoIP calls
Change-Id: Ic67abaeed0ea09f08ad5586cebe858e74fe21af9