Added missing A2DP priority on java alarm service

Running GKI timer engine via JAVA alarm service was causing severe
timer preemption at times which affects A2DP media task timer. This in
turn was stressing the compensation logic towards UIPC resulting in
very bursty reads of up to 40 UIPC frames at a time. This led to
instabilities on the UIPC pipe and trickled upwards in audio framework.
Inclusion of java alarm thread in A2DP high priority thread list results
in a much smoother data flow for entire A2DP data path and improved
audio quality.

Bug: 17520043
Change-Id: I7cea6ec64aa5b973b5fff767389a8827e681619e