Fix clang-tidy warnings in audio and playerservice.

* Add explicit keyword to conversion constructors.
Bug: 28341362
* Use const reference type for read-only parameters.
Bug: 30407689
Test: build with WITH_TIDY=1

Change-Id: I265f3b094e08d5705b506b3fbba51439c134af84
diff --git a/include/media/IAudioPolicyService.h b/include/media/IAudioPolicyService.h
index 0e9e3bc..ef15a0c 100644
--- a/include/media/IAudioPolicyService.h
+++ b/include/media/IAudioPolicyService.h
@@ -160,7 +160,7 @@
 
     virtual audio_mode_t getPhoneState() = 0;
 
-    virtual status_t registerPolicyMixes(Vector<AudioMix> mixes, bool registration) = 0;
+    virtual status_t registerPolicyMixes(const Vector<AudioMix>& mixes, bool registration) = 0;
 
     virtual status_t startAudioSource(const struct audio_port_config *source,
                                       const audio_attributes_t *attributes,