clearkey aidl: misc fixes

* accept default arguments in isCryptoSchemeSupported
* correctly concat secure stop id & data in getSecureStop(s)
* always return SW_SECURE_CRYPTO in getSecurityLevel
* SessionLibrary NO need to inherit RefBase
* compiler bug 215440148 workaround

Bug: 206804036
Test: atest MediaDrmClearkeyTest
Change-Id: I4952fcf4f8a2bfd5ddf6812257a310fec7bca52b