Handle UnicodeDecodeError in log_http_response

Similar to commit dec9c9f35 and log_curl_request,
this ignores decoding errors when logging response
headers by passing errors='ignore' to safe_encode.

Change-Id: Ic915a7d8334e9473f300c9db670a3a8f5cda8976
Closes-Bug: #1369756

glanceclient/common/http.py

@@ -130,7 +130,8 @@ class HTTPClient(object):
         if body:
             body = strutils.safe_decode(body)
             dump.extend([body, ''])
-        LOG.debug('\n'.join([strutils.safe_encode(x) for x in dump]))
+        LOG.debug('\n'.join([strutils.safe_encode(x, errors='ignore')
+                             for x in dump]))
 
     @staticmethod
     def encode_headers(headers):