Default ACLs created by the package have changed, guide needs updating

[Andreas Hasenack]

The ACL section at https://help.ubuntu.com/16.04/serverguide/openldap-server.html#openldap-server-acl needs updating because the default ACLs installed by the slapd package have changed.

For example, instead of (from the guide):
sudo ldapsearch -Q -LLL -Y EXTERNAL -H ldapi:/// -b cn=config '(olcDatabase={1}hdb)' olcAccess

dn: olcDatabase={1}hdb,cn=config
olcAccess: {0}to attrs=userPassword,shadowLastChange by self write by anonymous
              auth by dn="cn=admin,dc=example,dc=com" write by * none
olcAccess: {1}to dn.base="" by * read
olcAccess: {2}to * by self write by dn="cn=admin,dc=example,dc=com" write by *
  read

We now have (the s/hdb/mdb/ change is covered in bug #1689649):
$ sudo ldapsearch -Q -LLL -Y EXTERNAL -H ldapi:/// -b cn=config '(olcDatabase={1}mdb)' olcAccess
dn: olcDatabase={1}mdb,cn=config
olcAccess: {0}to attrs=userPassword by self write by anonymous auth by * none
olcAccess: {1}to attrs=shadowLastChange by self write by * read
olcAccess: {2}to * by * read