[FedCM] Fix crash when ShowAccountsDialog() completes the request

In cases like when we cannot show the Android bottomsheet, the request
is cancelled right away, so any method afterwards should assume that
Cleanup() maybe have been called. In this case, do not record that the
accounts have been shown, as nothing was actually shown.

Bug: 328945371
Change-Id: Iec962e2ea6e6246521f730129c452ffd11ef52a2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5363753


Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Nicolás Peña <npm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1271204}