AlarmTool: handle automatic solve with alarms owned by system user

Business templates are installed by system user, which is a special
user not returned by getWrappedOwner. Because of this, the "fixing
problems or activating a disabled alarm is not allowed" error was
raised when checking if the owner of the alarm has manage portal
permission on the alarm.

This switches the implementation to explicit creation of the user
when user id is the system user, so that we have a user with the
permission to solve the alarm.