Fix audio record pre-processing

proc_buf_out consistently initialized.
intermediate scratch buffers consistently initialized.
prevent read failure from overwriting memory.

Test: POC, CTS, camera record
Bug: 62873231
Change-Id: Ie26e12a419a5819c1c5c3a0bcf1876d6d7aca686
(cherry picked from commit 6d7b330c27efba944817e647955da48e54fd74eb)

static int do_out_standby_l(struct stream_out *out)
{
 struct audio_device *adev = out->dev;
 int status = 0;

    out->standby = true;
    out_close_pcm_devices(out);
    status = stop_output_stream(out);

 return status;
}

static int do_out_standby_l(struct stream_out *out)
{
 struct audio_device *adev = out->dev;
 int status = 0;

    out->standby = true;
    out_close_pcm_devices(out);
    status = stop_output_stream(out);

 return status;
}
