Description of problem:
When creating an entry with attributes matching the automemberFilter of an auto
membership definition, but for which the autoMemberDefaultGroup doesn't exist,
the entry is created successfully, without any error or even without warning

Version-Release number of selected component (if applicable):
389-ds-base-1.3.9.1-10.el7.x86_64
and 389-ds-base-1.3.10.1-2.el7.x86_64

How reproducible:
always

Steps to Reproduce:
1. enable the memberof plugin
2. Add a configuration entry for the auto Membership Plugin,
autoMemberDefaultGroup value being a non existing group. For example :
dn: cn=test users,cn=Auto Membership Plugin,cn=plugins,cn=config
objectclass: autoMemberDefinition
autoMemberScope: ou=People,dc=example,dc=com
autoMemberFilter: objectclass=nsView
autoMemberDefaultGroup: cn=invalid group,ou=Groups,dc=example,dc=com
autoMemberGroupingAttr: uniqueMember:dn

cn=invalid group,ou=Groups,dc=example,dc=com does not exist

3. create en entry part of the autoMemberScope of the auto Membership plugin
definition, having an attribute matching the autoMemberFilter. For example :
dn: ou=test view,ou=People,dc=example,dc=com
objectClass: top
objectClass: organizationalUnit
objectClass: nsView
ou: test view
description: test view

Actual results:
The entry is added successfully

Expected results:
The operation should be rejected, or at least an error message should be
returned/logged to warn that the group to which the entry should be added does
not exist.


Additional info:
linked to https://pagure.io/389-ds-base/issue/50077 ??