Fix missing NDK session closed callback

NDK session closed callback is not coming when client calls session close api
if another client is also streaming at the same time. This is due to the
ACameraCaptureSession destructor not being called as the busysession
strong pointer is not being freed due to missing onIdle callback.

Flag: com.android.internal.camera.flags.camera_multi_client
Bug: 392933426
Test: Run CTS test SharedCameraTest
Change-Id: I2325d58f8592a12bf3097ed1bcdbc4980dd39d3f