ART: Add missing GetInterfaceMethodIfProxy

Add missing uses of GetInterfaceMethodIfProxy in reflection code.

Add a test case for a JNI call to a proxy method.

Bug: https://code.google.com/p/android-developer-preview/issues/detail?id=2973
Bug: 23886441
Change-Id: I5b66b64b5561fcee15d0314707d67e8abc02ce5b