Add support for env var OS_INSECURE to control secure auth with keystone

To force secure auth, set 'export OS_INSECURE='
To force insecure auth, set 'export OS_INSECURE=1'
Currently, only insecure auth will work
If secure auth is forced, certificate would need be provided, support for which
will be added soon

Change-Id: I67cb41f40bc64552340571b5fe70a22fbc2b0ebd