Fix zuul_swift_upload to use old MAGIC_MIME const

The magic bindings updated to not prefix their constants with
MAGIC. Centos has an old version so we need to use the old constant
names (which are backwards compatible).

I've tested this on centos6 and ubuntu 12.04

Change-Id: Ic64c7395323e7583b37cf624d062cc3f40c89893
Merge "Fix zuul_swift_upload to use old MAGIC_MIME const"