Ticket 49356 - mapping tree crash can occur during tot init
    
    Bug Description:  Two faults were found in the handling of the mapping
    tree of 389 directory server. The first fault was that the tree-free
    check was not performed atomically and may cause an incorrect operations
    error to be returned. The second was that during a total init the referral
    would not lock the be, but the pw_verify code assumed a be was locked.
    This caused a segfault.
    
    Fix Description:  Fix the freed check to use atomics. Fix the pw_verify
    to assert be is NULL (which is correct, there is no backend).
    
    https://pagure.io/389-ds-base/issue/49356
    
    Author: wibrown
    
    Review by: mreynolds (THanks!)