Fix cloud-init runcmd to be exec friendly

Fix cloud-init runcmd to be exec friendly

Can't use colon builtin apparently, or you'll get this:
/var/lib/cloud/instance/scripts/runcmd: line 2:
 {setenforce 0 > /dev/null 2>&1 ||:: No such file or directory

Added cloud-init debug output to get the above, copied from:
http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/view/head:/doc/examples/cloud-config-chef.txt

Change-Id: I341cf73bc9a0f843d7ab8c99a9d15e1d514654e7
Signed-off-by: Jeff Peeler <jpeeler@redhat.com>