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/services/audiopolicy/service/AudioPolicyEffects.h b/services/audiopolicy/service/AudioPolicyEffects.h
index f68966f..9428409 100644
--- a/services/audiopolicy/service/AudioPolicyEffects.h
+++ b/services/audiopolicy/service/AudioPolicyEffects.h
@@ -136,7 +136,7 @@
     // class to store voctor of AudioEffects
     class EffectVector {
     public:
-        EffectVector(audio_session_t session) : mSessionId(session), mRefCount(0) {}
+        explicit EffectVector(audio_session_t session) : mSessionId(session), mRefCount(0) {}
         /*virtual*/ ~EffectVector() {}
 
         // Enable or disable all effects in effect vector