--edit-managed sets a header x-designate-edit-managed-records
that indicates the current request wishes to modify managed records
such as the SOA or NS record created for a zone. This is only used
by the recordset update and delete API methods so can be removed
elsewhere.
Closes-Bug: 1928411
Change-Id: I18bfdae045c8b5e589075865eb024cee4852d8f9