Expose status, add backward compat in tests and remove unused code

* Expose release and offline statuses in CdmEngine.

  [ Merge of http://go/wvgerrit/14616 ]

  This will allow me to make some intelligent decisions in the new CE
  CDM implementation without having to duplicate all the information
  known in the lower levels.

* Account for backward compat support in tests

  [ Merge of http://go/wvgerrit/14621 ]

  One test ensures that device path backward compatibility is working,
  while another assumes it is used.

  This fixes test results when
  Properties::security_level_path_backward_compatibility_support()
  is false.

  Previously, the CE CDM did not run these tests, and so this went
  unnoticed.

* Remove Lock::Try, which is not used.

  [ Merge of http://go/wvgerrit/14624 ]

Change-Id: Id18cf1f5b18c7322b8b636819276361af225734f

libwvdrmengine/cdm/core/include/cdm_session.h

@@ -101,6 +101,9 @@ class CdmSession {
     is_usage_update_needed_ = false;
   }
 
+  virtual bool is_release() { return is_release_; }
+  virtual bool is_offline() { return is_offline_; }
+
   // ReleaseCrypto() - Closes the underlying crypto session but leaves this
   // object alive. It is invalid to call any method that requires a crypto
   // session after calling this. Since calling this renders this object mostly