Revert "vp9-svc: Fix to first superframe when inter_layer is off."

Revert "vp9-svc: Fix to first superframe when inter_layer is off."

This reverts commit 5cc8df5bcfe49fbfca21ee57401c7807c048751b.

Reason for revert: <INSERT REASONING HERE>
We need to do this on all key frames in the stream (not just the first one). Will make another cleaner change for this.

Original change's description:
> vp9-svc: Fix to first superframe when inter_layer is off.
>
> When the application selects the setting INTER_LAYER_PRED_OFF
> each spatial stream should be decodeable separately.
> For this we need to force key frames on all spatial layers
> on the first superframe.
>
> In order to maintain the quality at the beginning of the stream
> the active_worst for spatial layer of the second superframe is set
> to the last_QP of the correspondng spatial layer of the first superframe.
> Also make sure nonrd_keyframe is set for non-base spatial layers.
>
> Change only affects SVC mode wit number_spatial_layers > 1 and
> svc->disable_inter_layer_pred == INTER_LAYER_PRED_OFF.
> And only affects first and second frame of sequence.
>
> Change-Id: I8ee9a0873ab1d3a02515774571f719617771ad41

TBR=marpan@google.com,builds@webmproject.org,jianj@google.com

Change-Id: If73d9f3932224fc6751e773763adf7e8ee67d17f
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