Admin First Byte Timeout setting does not work for admin URLs including `checkout` string.

[pawel-siejba]

In the recv VCL snippet, something is considered an admin URL if it has the ####ADMIN_PATH#### AND req.url ~ "/(checkout|customer/section/load)" is false.

However, some admin paths, e.g config, contain the 'checkout' string in them.
For example Admin > Config > Sales > Checkout.

The following is the if/else statement with the bug present:
https://github.com/fastly/fastly-magento2/blob/master/etc/vcl_snippets/recv.vcl#L154
if (!req.http.x-long-cache && req.url ~ "/(checkout|customer/section/load)") { set req.http.x-pass = "1"; # Pass all admin actions # ####ADMIN_PATH#### is replaced with value of frontName from app/etc/env.php } else if ( req.url ~ "^/(index\.php/)?####ADMIN_PATH####/" ) { set req.http.x-pass = "1"; set req.http.magento-admin-path = "1"; }

This bug essentially means, that later, all of the parts of VCL relying on req.http.magento-admin-path won't work for these select few Admin paths containing checkout string in the URL.

Currently there's one snippet relying on it - setting the admin byte timeout.