issue_server_cert: avoid application of str to bytes

Part of: https://pagure.io/freeipa/issue/7131

Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>

ipaserver/install/certs.py

@@ -437,7 +437,7 @@ class CertDB(object):
             client_keyfile=paths.RA_AGENT_KEY,
             **params)
         http_status, _http_headers, http_body = result
-        logger.debug("CA answer: %s", http_body)
+        logger.debug("CA answer: %r", http_body)
 
         if http_status != 200:
             raise CertificateOperationError(