Initialize volume as 0 for volume control effect.

If a effect is going to be the effect that controls volume, initialize
the volume as 0 for safe ramping. The actual volume is always set when
preparing the tracks. However, the effect can still be enabled after
that and before the next tracks preparation. In that case, initialize
the volume as 0 can help avoid sound blast out when the effect is
enabled.

Bug: 328598362
Test: atest AudioEffectTest
Test: repo steps in the bug
Change-Id: I24eb3c7f21dee8dd4bf9337010b05c09f8f00873