audiohal: Always load A2DP module locally

This makes legitimate unix socket interaction between A2DP
module and the Bluetooth stack.

Implemented by allowing both "local" and "hidl" interface
wrappers to co-exist for devices and streams. A "hybrid" device
factory is introduced to create an appropriate implementation
of a device depending on the requested module name.

Bug: 37640821
Test: Play Music over BT headset
Change-Id: I5592961dd5b56840418fb122680979d11a261b6c
diff --git a/media/libaudiohal/DevicesFactoryHalHidl.h b/media/libaudiohal/DevicesFactoryHalHidl.h
index a26dec1..e2f1ad1 100644
--- a/media/libaudiohal/DevicesFactoryHalHidl.h
+++ b/media/libaudiohal/DevicesFactoryHalHidl.h
@@ -36,7 +36,7 @@
     virtual status_t openDevice(const char *name, sp<DeviceHalInterface> *device);
 
   private:
-    friend class DevicesFactoryHalInterface;
+    friend class DevicesFactoryHalHybrid;
 
     sp<IDevicesFactory> mDevicesFactory;