Baremetal deploy helper sets ODIRECT.

Baremetal deploy helper should set oflag=direct when dd'ing images onto
iSCSI targets, so that it doesn't waste the local page cache.

Fixes bug 1114633.

Change-Id: Ia674afb34aff7b842cfcd520ecb7b75dc21944fa

bin/nova-baremetal-deploy-helper

@@ -121,6 +121,7 @@ def dd(src, dst):
                   'if=%s' % src,
                   'of=%s' % dst,
                   'bs=1M',
+                  'oflag=direct',
                   run_as_root=True,
                   check_exit_code=[0])