Only detach parent interface when SurfaceView detached from window.

Conceptually, remote views added from windowless windows should remain
within the host side's view hierarchy, even when the host view becomes
invisible. Therefore, they should only disconnect when the host view is
detached from the window.

Flag: EXEMPT bugfix
Bug: 399009879
Test: launch sample app then back to home, resume app back and verify
the mParentInterface remain connected. Also verify the mParentInterface
will be removed when host app finished.

Change-Id: I1fd89bb0a27dca07d3bc779685e35d89bd70f37b