Issue 5734 - RFE - Exclude pwdFailureTime and ContextCSN (#5735)

Bug Description: A customer reported an issue with openldap to 389ds migration. This was due to
their openldap instance using a number of openldap attributes that I had not encountered in other
migrations.

These attributes are operational to openldap only and can be safely excluded.

Fix Description: Exclude pwdFailureTime and ContextCSN

fixes: #5734

Author: William Brown <william@blackhats.net.au>

Review by: ???

src/lib389/lib389/migrate/plan.py

@@ -662,13 +662,16 @@ def __init__(self, inst, olschema=None, oldatabases=None, ldifs=None, skip_schem
             [
                 # Core openldap attrs that we can't use, and don't matter.
                 'entrycsn',
+                'contextcsn',
                 'structuralobjectclass',
                 # pwd attributes from ppolicy which are not supported.
                 'pwdattribute',
                 'pwdcheckquality',
                 'pwdsafemodify',
                 'pwdcheckmodule',
                 'pwdmaxrecordedfailure',
+                # ppolicy attr that isn't in schema that isn't supported.
+                'pwdfailuretime',
                 # dds attributes we don't support
                 'dgidentity',
                 'dgauthz'