Ticket #129 - Should only update modifyTimestamp/modifiersName on MODIFY ops
    
    Bug Description:  Some internal updates should not rewrite the modifersname and timestamp
    
    Fix Description:  Since the orginal bug was filed, we created a new pblock flag
                      to "skip modifier attrs" updates.  But we did not have the option
                      of setting this flag from a plugin.
    
                      So, while this has already been fixed in regards to password
                      policy.  I added a set pblock function, which allows plugins
                      to set this flag.  I also used it in the acctpolicy plugin.