Import only modules and update tox.ini

As stated in the OpenStack Hacking Guidelines, it is prefered
that only modules should be imported.

Also updated tox.ini to ignore opestack/common among others.

Change-Id: I2f0a603c31052eadee581c11880c0ec6bd392829

glanceclient/common/https.py

@@ -47,11 +47,10 @@ try:
     else:
         raise ImportError
 except ImportError:
-    try:
-        from httplib import HTTPSConnection
-    except ImportError:
-        from http.client import HTTPSConnection
-    from OpenSSL.SSL import Connection as Connection
+    from OpenSSL import SSL
+    from six.moves import http_client
+    HTTPSConnection = http_client.HTTPSConnection
+    Connection = SSL.Connection
 
 
 from glanceclient import exc