Crash in SystemUI in Multi-User case for PIP.

Description:
04-10 13:50:21.197 1010145 10252 10252 E AndroidRuntime: Process: com.android.systemui, PID: 10252
04-10 13:50:21.197 1010145 10252 10252 E AndroidRuntime: java.lang.IllegalStateException: Existing input consumer found with name: pip_input_consumer, display: 0
04-10 13:50:21.197 1010145 10252 10252 E AndroidRuntime: 	at android.os.Parcel.createExceptionOrNull(Parcel.java:2382)
04-10 13:50:21.197 1010145 10252 10252 E AndroidRuntime: 	at android.os.Parcel.createException(Parcel.java:2358)
04-10 13:50:21.197 1010145 10252 10252 E AndroidRuntime: 	at android.os.Parcel.readException(Parcel.java:2341)
04-10 13:50:21.197 1010145 10252 10252 E AndroidRuntime: 	at android.os.Parcel.readException(Parcel.java:2283)
04-10 13:50:21.197 1010145 10252 10252 E AndroidRuntime: 	at android.view.IWindowManager$Stub$Proxy.createInputConsumer(IWindowManager.java:5175)
04-10 13:50:21.197 1010145 10252 10252 E AndroidRuntime: 	at com.android.systemui.shared.system.InputConsumerController.registerInputConsumer(InputConsumerController.java:165)

Crash is occurring. If two users are present. Open any app in PIP. Then keep on moving it to PIP to non-PIP and non-PIP to PIP.
Eventually crash will happen because onActivity Pinned is getting called 2 times. pip_input_consumer that is already present, is getting created again.

Fix: Do nothing if user is different.

Change-Id: Ie49d7ed525b5c5583c96f54ed3fb0901ff76c6ec
Signed-off-by: pioush garg <pioushkumar1992@gmail.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>