vendor: Pin github.com/optiopay/kafka to commit before fork

[christarazi]

This dependency has been causing a lot of issues for those who are
consuming the Cilium code as a module. It required consumers to
duplicate the replace directive for optiopay/kafka in their
respective go.mod file.

This commit fixes this by pinning the original optiopay/kafka to the
commit when it was forked by Cilium developers (and hence the replace
directive).

Suggested-by: Glib Smaga code@gsmaga.com
Signed-off-by: Chris Tarazi chris@isovalent.com

[christarazi]

If this fixes it, then we should update the docs and references such as https://github.com/cilium/client-examples.

[christarazi]

Here's how it was tested:

❯ cat --plain main.go go.mod
package main

import (
    "fmt"

    "github.com/cilium/cilium/pkg/hubble/observer/observeroption"
)

func main() {
    var opt observeroption.Option
    fmt.Println(opt)
}
module f

go 1.16

replace github.com/cilium/cilium => /home/chris/code/cilium/cilium

require github.com/cilium/cilium v0.0.0-00010101000000-000000000000

/tmp/f
❯ go mod tidy -v
go: downloading github.com/sirupsen/logrus v1.7.0
...
go: downloading golang.org/x/mod v0.3.0

/tmp/f 9s
❯ go clean -modcache ./

# Switched the repo back to master

/tmp/f
❯ go mod tidy -v
go: github.com/cilium/cilium@v0.0.0-00010101000000-000000000000 requires
        github.com/optiopay/kafka@v0.0.0-00010101000000-000000000000: invalid version: unknown revision 000000000000

[tklauser]

Changes in go.mod only with no effects on vendor/, thus no need to run full CI. Marked as ready to merge.