Stop checking whether the speakerphone is on

Recent changes in the audio framework have separated out speakerphone
requests by calling package. Therefore, if some other app turns
bluetooth on and we get notified about it after isSpeakerphoneOn starts
returning false, we may not clear our request for speakerphone,
thereby causing the device to return to speakerphone mode the next time
BT is turned off.

Fix this by no longer checking isSpeakerphoneOn. However, in order to
prevent us from lodging our own request when an external app turns
speakerphone on, start turning on speakerphone upon user request rather
than in the entry method of the speakerphone state.

Fixes: 162289995
Test: atest CallAudioRouteTransitionTests, manual

Change-Id: I4c52307a4937b61eebe18cf2dc1a881bfd834b34