Changed local refs in JNI to ScopedLocalRef

Objects were leaking in InputManagerService JNI since there were calls
from the native process without clearing the local reference.
Converted the references to ScopedLocalRef so they get removed
automatically when out of scope.

Test: No longer leaking IWindow when opening/closing apps
Fixes: 131355264
Change-Id: I054faeb83360d7c43c3491680c3a39ba0b0c8351