If passwd_tries is less than 1, check_user() will always return

If passwd_tries is less than 1, check_user() will always return
false (since the user didn't authenticate).  The normal reason for
this is an authentication error but in this case no authentication
was tries so no warning message has been displayed to the user.  If
the user wasn't given a chance to authenticate, set inform_user to
true when calling log_denial() from sudoers_policy_main().

An alternate approach would be for check_user() to return true
in this case but seems more confusing.