Fix missing libffi-devel for python-glanceclient

python-glanceclient is failing to install on rhel6 with a dependency
chain from pip as

  cryptography>=0.2.1 (from pyOpenSSL>=0.11->python-glanceclient==0.12.0.56.gb8a850c)

cryptography requires libffi-devel to build.  I'm not sure what
changed, but remove it from "testonly" so it is always installed.

However, RHEL6 includes this in the optional repo, so we enable this
repo in the fixup script.

Change-Id: I9da0e91b75f41578861ee9685b8c7e91dd12dae7
diff --git a/files/apts/glance b/files/apts/glance
index 22787bc..6dc878e 100644
--- a/files/apts/glance
+++ b/files/apts/glance
@@ -1,5 +1,5 @@
 gcc
-libffi-dev          # testonly
+libffi-dev
 libmysqlclient-dev  # testonly
 libpq-dev           # testonly
 libssl-dev          # testonly