cert: fix CLI output of cert_remove_hold

cert_remove_hold uses output params instead of exceptions to convey
unsuccessful result. Move the output params to the client side before
the command is fixed to use exceptions.

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

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

ipaclient/plugins/cert.py

@@ -23,7 +23,7 @@ from ipaclient.frontend import MethodOverride
 from ipalib import errors
 from ipalib import x509
 from ipalib import util
-from ipalib.parameters import File
+from ipalib.parameters import File, Flag, Str
 from ipalib.plugable import Registry
 from ipalib.text import _
 
@@ -54,6 +54,18 @@ class cert_show(MethodOverride):
             return super(cert_show, self).forward(*keys, **options)
 
 
+@register(override=True)
+class cert_remove_hold(MethodOverride):
+    has_output_params = (
+        Flag('unrevoked',
+            label=_('Unrevoked'),
+        ),
+        Str('error_string',
+            label=_('Error'),
+        ),
+    )
+
+
 @register(override=True)
 class cert_find(MethodOverride):
     takes_options = (