Clean up salt-bootstrap: 1) stable works for rhel7 2) use urllib everywhere

Signed-off-by: Dan Mick <dan.mick@inktank.com>
Oops, nope, rhel7 not quite done yet

Signed-off-by: Dan Mick <dan.mick@inktank.com>
Missed edit of path for bootstrap

Signed-off-by: Dan Mick <dan.mick@inktank.com>