Fix problem in AudioEffect::command() status.

The *pReplyData argument of the command() function was left unitialized by EffectHandle::command()
when command was EFFECT_CMD_ENABLE, EFFECT_CMD_DISABLE and EFFECT_CMD_SET_PARAM_COMMIT.

Change-Id: I91a19817ead2a8cfbdd8e2d77ca270c7ce9d5bd4