Don't check the certificate when transloading

This allows the download of images via https even if the cert is self-signed.
Actually set the cookie prefix

When COOKIE_PREFIX was not shm (the default) the script tried to read cookies prefixed with the new prefix but the script was setting the old default prefix from before the constants were implemented.
Merge pull request #309 from HungryFeline/patch-3

Don't check the certificate when transloading