VTS: update CSD validation for Video Encoder Test

Zero size CSD is considered same as CSD not received.
This patch also updates the CSD check condition for
VP9, VP8 and H263.

Test: atest VtsHalMediaC2V1_0TargetVideoEncTest

Bug: 157572658
Change-Id: I31d1c339065da60a6b8e2e28256399229159d23f