ipa-replica-manage: handle missing attributes
If nsds5replicalastupdateend is not yet present,
ipa-replica-manage will backtrace as it tries to retrieve that
attribute unconditionally.
Gracefully handle that situation.
Fixes: https://pagure.io/freeipa/issue/8605
Signed-off-by: François Cami <fcami@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>
Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>