Use AudioManager.MODE_NORMAL when selecting account from dialog.

Because the "Call with" dialog is part of the InCallUI, by default it
uses the audio mode of the InCallUI, which is MODE_IN_CALL. In order to
make TalkBack audible for the dialog, use AudioManager.MODE_NORMAL just
for the PRE_DIAL_WAIT case.

Bug: 18327621
Change-Id: Ie79053759fb84e3fff51a6bc63e8cc12291486cf