Fix argparse issue for RHEL 6.5.

Since RHEL 6.5 uses Python 2.6, which lacks argparse,
they need to be installed to ensure that os-apply-config
and os-refresh-config work properly.

Change-Id: I80dcce56d00fc6f1240a5fcccd425cc2b4db29d5
Merge "Fix argparse issue for RHEL 6.5."