Make sure user created notice doesn't auto-vanish

The "user created" notice contains a 4-character random password, which
the manager who created the account is going to need to write down. Now
that success messages automatically disappear after 10 seconds, that
could lead to the manager not writing down the new password in time
before it disappears, which is obviously bad. We'll use INFO rather than
SUCCESS for this message; info is for messages that need to be manually
acknowledged (by clicking their close button).