Fix ConfirmCredential is not presented before trusting cert installed by PO/DO

- Show ConfirmCredential in TrustedCredentialsSettings when Trust button is clicked
  for the very first time since the activity launched
- Warning activity (work mode off, crpyto-aware) should not be shown when the activity is started. Also fixed it here.

Bug: 28619980
Change-Id: I084b70883c087376e437a9ad3238d7c3313a0a17