Do not show 2nd FingerprintErrorDialog

When fingerprint enrollment is stopped because of credential timeout, it
pops a FingerprintErrorDialog, and this error dialog triggers
onWindowFocusChanged(), and the 2nd FingerprintErrorDialog is shown. To
fix this case, checking mIsCanceled flag do nothing  in
onWindowFocusChanged() method.

On the first dialog, the 'Try again' button relaunch activity with new
Intent, and it causes that activity result fails to pass back to caller.
To fix this bug, add FLAG_ACTIVITY_FORWARD_RESULT on new Intent to pass
result back.

Bug: 248165760
Test: Manually test credential timeout behavior and dialog buttons
Test: Manually test enrollment process has been cancelled for scenarios,
      like "Swipe down Notification Shade" and "Recents"
Test: robo test for FingerprintEnrollEnrollingTest
Change-Id: I4441ba026db9b594f1d6184280668a374126a2fb