Clarify wording of MediaCrypto exception "ERROR_NO_KEY"
Clarify wording of MediaCrypto exception "ERROR_NO_KEY"

related-to-bug: 20857014
Change-Id: I13204528ec44cda76a721f4d9f6021c1435921ac

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base