Slight gssapi init refactor to make mock easier

Author: dpkp

kafka/sasl/gssapi.py

@@ -26,14 +26,15 @@ def __init__(self, **config):
             raise ValueError('sasl_kerberos_service_name or sasl_kerberos_name required for GSSAPI sasl configuration')
         self._is_done = False
         self._is_authenticated = False
+        self.gssapi_name = None
         if config.get('sasl_kerberos_name', None) is not None:
             self.auth_id = str(config['sasl_kerberos_name'])
+            if isinstance(config['sasl_kerberos_name'], gssapi.Name):
+                self.gssapi_name = config['sasl_kerberos_name']
         else:
             kerberos_domain_name = config.get('sasl_kerberos_domain_name', '') or config.get('host', '')
             self.auth_id = config['sasl_kerberos_service_name'] + '@' + kerberos_domain_name
-        if isinstance(config.get('sasl_kerberos_name', None), gssapi.Name):
-            self.gssapi_name = config['sasl_kerberos_name']
-        else:
+        if self.gssapi_name is None:
             self.gssapi_name = gssapi.Name(self.auth_id, name_type=gssapi.NameType.hostbased_service).canonicalize(gssapi.MechType.kerberos)
         self._client_ctx = gssapi.SecurityContext(name=self.gssapi_name, usage='initiate')
         self._next_token = self._client_ctx.step(None)