Fix warning about recursive loading of libmedia_jni.so

JNI register methods were resolving classes to initialize fieldID's
and methodID's for native JNI use. Those classes may have static
initializers which call System.loadLibrary("libmedia_jni.so"), but the
library is already in the process of being loaded.

Bug: 180829511
Test: TH
Test: boot blueline observe no output from "adb logcat -d | grep recursive"
Change-Id: I47d40bc06457a9550bd5855f6f8d031ddc465b47