Increase lock scope to protect variables

Ensure that the variable is locked throughout its lifetime.

Test: atest android.media.audio.cts.AudioEffectTest android.media.audio.cts.AudioPreProcessingTest android.media.audio.cts.BassBoostTest android.media.audio.cts.EnvReverbTest android.media.audio.cts.EqualizerTest android.media.audio.cts.LoudnessEnhancerTest android.media.audio.cts.PresetReverbTest android.media.audio.cts.VirtualizerTest android.media.audio.cts.VisualizerTest
Change-Id: I0bcaaa43c24df2afee1cbef278231ec94833c076
Signed-off-by: zhanglina1 <zhanglina1@xiaomi.corp-partner.google.com>