[ Merge of https://widevine-internal-review.googlesource.com/#/c/10659/
from the widevine cdm repo. ]
CdmEngine::CancelKeyRequest would earlier release keys by closing and
reopening a crypto session. Behavior has been changed to just close
the session.
b/15984869
Change-Id: I92a1f82fd4a97b5510596d4bc69bf07406cee606