Upload images with --file instead of stdin

This is more likely how people will actually upload their images, but
it also prevents the "osc as a service" feature from working because
stdin isn't proxied (of course). So just convert our uses of "image
create" to use --file instead of stdin.

Change-Id: I7205eb0100ba7406650ed609cf517cba2c8d30aa
1 file changed