sdk: Replace httplib with pycurl

Currently we use the Python httplib module to handle the HTTP connection
with the server. Unfortunatelly this module doesn't support any
interesting authentication mechanism. In the future we want to add
support for Kerberos, for example. As a first step this patch replaces
httplib with the pycurl.

Change-Id: I7fa93cef1b8ca0deb5bdbc02c35ab604e11b4570
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>