Some entity types (like Properties) require special permission for altering terms. When the "clear" flag is applied in wbeditentity, these permissions need to be checked.

Note: A typical use case for the "clear" flag is load-modify-save, in which case all the terms may be restored as they were. In that case, the permissions would not need to be checked. This optimization is however beyond the scope of this ticket. See T171484 for that.