[ Merge of http://go/wvgerrit/122103 ]
When in CTR mode an encryption pattern should no longer be specified.
This will address failures in Cdm/WvCenc30Test.DecryptionTest/* and
Cdm/WvCenc30SwitchCipherModeTest.DecryptionTest/*
Bug: 181693982
Test: WV unit/integration tests
Change-Id: Iecbf28b51115501439aebf057056657c796896ae