Only load service account of kubeconfig was not found (#311)

kr8s/_auth.py

@@ -58,7 +58,7 @@ async def reauthenticate(self) -> None:
             else:
                 if self._kubeconfig is not False:
                     await self._load_kubeconfig()
-                if self._serviceaccount:
+                if self._serviceaccount and not self.server:
                     await self._load_service_account()
             if not self.server:
                 raise ValueError("Unable to find valid credentials")