upload: making it faster on el6

Removing at all the usage of tarlib and gzip which are
really slow on Python 2.6

Change-Id: Ie7a1cf9757429e8cf77745b39a4c1b9efeab6169
Bug-Url: https://bugzilla.redhat.com/1150922
Signed-off-by: Simone Tiraboschi <stirabos@redhat.com>