client: ignore override errors in command overrides

This fixes API initialization errors when the remote server does not have
the overriden command.

https://fedorahosted.org/freeipa/ticket/4739

Reviewed-By: David Kupka <dkupka@redhat.com>

ipaclient/plugins/automember.py

@@ -25,7 +25,7 @@ from ipalib.text import _
 register = Registry()
 
 
-@register(override=True)
+@register(override=True, no_fail=True)
 class automember_add_condition(MethodOverride):
     has_output_params = (
         Str('failed',