Ticket 47569 - ACIs do not allow attribute subtypes in targetattr keyword
    
    When validating the targetattr ACI keyword, we check if the attribute
    is defined in the schema.  This schema check fails if the attribute
    has a subtype present.
    
    This patch makes the attribute syntax lookup function check if a
    subtype was specified before performing the looking.  If a subtype
    is specified, it is stripped off and we just use the base attribute
    name to lookup the syntax from the hashtable.