The upgraded adclient 5.4.1 a.k.a Suite 2017.1 has problem to remove AD computer object out from AD infrastructure with command 'adleave -r -u <delegated user>' executed, even the <delegated user> has "Delete Computer Objects" permission granted on AD computer container.

Cause: 

The LDAP flag used in the DELETE request sent to AD is changed to LDAP_SERVER_TREE_DELETE_OID, and LDAP_SERVER_EXTENDED_DN_OID was used in old times. 

The LDAP_SERVER_TREE_DELETE_OID control is used with an extended LDAP delete function to delete an entire subtree in the directory

Hence "Delete subtree" right to Descendant Computer object on the container/OU that the computer object locate is also needed.

Workaround: 

Both "Delete subtree" and "Delete compute objects" permissions are required to remove a computer object with adleave command.

References: (provided as a courtesy) 
https://msdn.microsoft.com/en-us/library/aa366991(v=vs.85).aspx
http://ijustdoit.eu/ad-delegate-permissions-to-add-delete-move-computer-objects