Fix admin principal naming convention in README and entrypoint script

entrypoint.sh

@@ -47,14 +47,14 @@ EOF
 EOF
 
     cat > /var/lib/krb5kdc/kadm5.acl <<EOF
-${ADMIN_PRINCIPAL}/admin@${REALM} *
+${ADMIN_PRINCIPAL}@${REALM} *
 EOF
 
     cp /var/lib/krb5kdc/krb5.conf /etc/krb5.conf
 
     echo "Initializing Kerberos realm ${REALM}..."
     KRB5_KDC_PROFILE=/var/lib/krb5kdc/kdc.conf kdb5_util create -s -P "${MASTER_PASSWORD}" -r "${REALM}"
-    KRB5_KDC_PROFILE=/var/lib/krb5kdc/kdc.conf kadmin.local -q "addprinc -pw ${ADMIN_PASSWORD} ${ADMIN_PRINCIPAL}/admin@${REALM}"
+    KRB5_KDC_PROFILE=/var/lib/krb5kdc/kdc.conf kadmin.local -q "addprinc -pw ${ADMIN_PASSWORD} ${ADMIN_PRINCIPAL}@${REALM}"
     echo "Realm initialized."
 else
     echo "Realm already initialized, skipping."