Merge from Widevine repo of http://go/wvgerrit/101143
This CL removes the check for a decrypt hash error when CopyBuffer is
used instead of DecryptCenc because a key was not selected.
We also remove the attempt to check the decrypt hash when there are
multiple buffers, because that is not well defined behavior.
Bug: 155185867
Bug: 155192141
Test: ran unit tests on taimen and on v16 reference oemcrypto
Change-Id: I640e904e256f0913ca606bb5db891430b23f44a3