pylint: Ignore usage of 'unicode' before assignment

New versions of pylint ignore Python 2 functions and types, evaluating
'unicode' as "undefined". ansible-freeipa will always define 'unicode'
when running under Python 3, and it is always defined under Python 2.

This patch fixes these false positives.

roles/ipareplica/library/ipareplica_prepare.py

@@ -658,7 +658,7 @@ def main():
         # Check authorization
         result = remote_api.Command['hostgroup_find'](
             cn=u'ipaservers',
-            host=[unicode(api.env.host)]
+            host=[unicode(api.env.host)]  # pylint: disable=E0606
         )['result']
         add_to_ipaservers = not result