Remove the frame rate factor for key frame size.
When temporal layers is used (i.e., number_of_layers > 1), we don't use the frame rate boost for setting the key frame target size. The factor was forcing the target size to be always at its minimum (2* per_frame_bandwidth) for low frame rates (i.e., base layer frame rate). Generally we should modify or remove this frame rate factor; for now we turn if off for number_of_layers > 1. Change-Id: Ia5acf406c9b2f634d30ac2473adc7b9bf2e7e6c6