Don't stream non-binary requests

Setting stream=True with requests can lead to issues
with not closing the connection so the urllib3 connection
pool is not freed up, so only set stream=True if making
a request with application/octet-stream content-type.

See the body-content-workflow and keep-alive sections
in the requests docs here for more information:

http://docs.python-requests.org/en/latest/user/advanced/

Note that commit dbb242b changed the response body_iter
code to potentially return a six.StringIO object rather
than the old ResponseBodyIterator class and since the
images client code is not converting the body_iter into
a dict using json.loads, we have to do that directly
in the _request method where the body_iter is
constructed.

Co-authored-by: Flavio Percoco <fpercoco@redhat.com>

Change-Id: I86572b69c4511f933c9676108190271874346302
Partial-Bug: #1341777

glanceclient/common/http.py

@@ -160,6 +160,7 @@ class HTTPClient(object):
                 data = chunk_body(data)
 
         headers['Content-Type'] = content_type
+        stream = True if content_type == 'application/octet-stream' else False
 
         # Note(flaper87): Before letting headers / url fly,
         # they should be encoded otherwise httplib will
@@ -172,7 +173,7 @@ class HTTPClient(object):
             resp = self.session.request(method,
                                         conn_url,
                                         data=data,
-                                        stream=True,
+                                        stream=stream,
                                         headers=headers,
                                         **kwargs)
         except requests.exceptions.Timeout as e:
@@ -217,6 +218,10 @@ class HTTPClient(object):
                 body_iter = resp.json()
             else:
                 body_iter = six.StringIO(content)
+                try:
+                    body_iter = json.loads(''.join([c for c in body_iter]))
+                except ValueError:
+                    body_iter = None
         return resp, body_iter
 
     def head(self, url, **kwargs):