when discard activities option on onActivityResult not call

[cuichanghao]

background activity may be killed by system.
line-sdk cannot return onActivityResult this case.

08-02 16:26:43.590 583-1162/? E/BufferQueueProducer: [myapp.debug/com.linecorp.linesdk.auth.internal.LineAuthenticationActivity#0] disconnect: not connected (req=1)

08-02 16:26:43.778 1214-1359/? E/WindowManager: win=Window{e1c109f u0 myapp.debug/com.linecorp.linesdk.auth.internal.LineAuthenticationActivity EXITING} destroySurfaces: appStopped=true win.mWindowRemovalAllowed=true win.mRemoveOnExit=true

08-02 16:26:43.791 583-1162/? E/BufferQueueProducer: [jp.naver.line.android/jp.naver.line.android.activity.channel.permission.ChannelPermissionApprovalActivity#0] disconnect: not connected (req=1)
08-02 16:26:43.792 583-1162/? E/SurfaceFlinger: Failed to find layer (myapp.debug/com.linecorp.linesdk.auth.internal.LineAuthenticationActivity#0) in layer parent (no-parent).