Fix https stack trace on python 3.4 client

When using the client with python 3.4 and no ssl compression the following
stack trace ocurrs:

 TypeError: startswith first arg must be bytes or a tuple of bytes, not str

Closes-bug: 1442883
Related-bug: 1357430
Change-Id: I8e28f0bb1f3e866f11851247ce31470ca8c2af4f

glanceclient/common/https.py

@@ -158,7 +158,9 @@ class HTTPSAdapter(adapters.HTTPAdapter):
         # NOTE(flaper87): Make sure the url is encoded, otherwise
         # python's standard httplib will fail with a TypeError.
         url = super(HTTPSAdapter, self).request_url(request, proxies)
-        return encodeutils.safe_encode(url)
+        if six.PY2:
+            url = encodeutils.safe_encode(url)
+        return url
 
     def _create_glance_httpsconnectionpool(self, url):
         kw = self.poolmanager.connection_kw