Add argparse for RHEL6

python2.6 doesn't have argparse, required by outfilter.py.  This
package is a dependency on cloud-init, so this problem is often masked
in many testing environments.

Change-Id: Ia564f1b8a7b540faa7bbdbd1a1a290c591901682
Merge "Add argparse for RHEL6"
Merge commit 'refs/changes/83/86083/2' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch
Merge commit 'refs/changes/74/106774/2' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch
Merge commit 'refs/changes/75/106775/1' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch
Merge commit 'refs/changes/45/107345/1' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch