libvpx

Updates to qp-regulate and rate correction factor.

Don't use the switch to gf_rate_correction factor when
temporal layers is used (i.e., cpi->oxcf.number_of_layers > 1).

In temporal layers, we prefer to avoid this as any frame
(e.g., base layer frame at anchor of pattern) may update
both last and golden (and possibly alt-ref), and so we would get
different rate correction factors within the same layer.

This change will make sure one rate correction factor exists for each layer.

Also, made some other code in qp-regulate that depends on
alt/golden update specific to the 1 layer case.

Change-Id: I41a6d085bd477f9307ef3b3c311695214273892c