Revert of Don't always downsample to 16kHz in the reverse stream in APM

Revert of Don't always downsample to 16kHz in the reverse stream in APM (patchset #4 id:60001 of https://codereview.webrtc.org/1865633005/ )

Reason for revert:
Creating a revert patch set of this to see if it could be causing the issues we see on the linux_ubsan_vptr bot now.
Not landing the revert just yet.

Original issue's description:
> Don't always downsample to 16kHz in the reverse stream in APM
> 
> The first approach landed here: https://codereview.webrtc.org/1773173002
> But it was partially reverted, because it affected the AEC performance, here: https://codereview.webrtc.org/1867483003/
> The main difference of this approach is that it doesn't use the 3-band splitting filter in the reverse stream, which seems to be the culprit of the AEC regression.
> Also, the 2-band splitting filter has been used for the 32kHz case for a long time without any problem, and this is expanded in the CL to cover the 48kHz case as well.
> 
> BUG=webrtc:5725
> TBR=tina.legrand@webrtc.org
> 
> Committed: https://crrev.com/eb3603bd5e72b3a941363c559ddea99ee71d510a
> Cr-Commit-Position: refs/heads/master@{#12451}

TBR=peah@webrtc.org,aluebs@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:5725

[tommi, 2016-04-24 22:22:17]

Created Revert of Don't always downsample to 16kHz in the reverse stream in APM

[tommi, 2016-04-24 22:31:33]

On 2016/04/24 22:22:17, tommi-webrtc wrote:
> Created Revert of Don't always downsample to 16kHz in the reverse stream in
APM

Looks unrelated. Not landing the revert.

[aluebs-webrtc, 2016-04-25 19:58:13]

On 2016/04/24 22:31:33, tommi-webrtc wrote:
> On 2016/04/24 22:22:17, tommi-webrtc wrote:
> > Created Revert of Don't always downsample to 16kHz in the reverse stream in
> APM
> 
> Looks unrelated. Not landing the revert.

:)