Fix coturn that was failing with newer Nomad/Docker

Coturn was failing to start with the following error:

failed to create task for container: failed to create shim task: OCI
runtime create failed: runc create failed: unable to start container
process: exec: "/usr/local/bin/docker-entrypoint.sh": permission denied:
unknown

It seems to be caused by the recent NixOS update.

Either because Docker/runc is now more strict when checking if the
entrypoint is executable [1]

And/or because Nomad may mount the secrets directory with "noexec" [2].

In any case, the "local" directory [2] looks more appropriate, because
it's shared with the task while not being accessible to other tasks.

[1] https://github.com/opencontainers/runc/issues/3715
[2] https://developer.hashicorp.com/nomad/docs/concepts/filesystem

cluster/prod/app/coturn/deploy/coturn.hcl

@@ -34,15 +34,13 @@ job "coturn" {
         ports = [ "prometheus", "turn_ctrl", "turn_data0", "turn_data1", "turn_data2",
                   "turn_data3", "turn_data4", "turn_data5", "turn_data6", "turn_data7",
                   "turn_data8", "turn_data9" ]
+        entrypoint = ["/local/docker-entrypoint.sh"]
         network_mode = "host"
-        volumes = [
-          "secrets/docker-entrypoint.sh:/usr/local/bin/docker-entrypoint.sh",
-        ]
       }
 
       template {
         data = file("../config/docker-entrypoint.sh")
-        destination = "secrets/docker-entrypoint.sh"
+        destination = "local/docker-entrypoint.sh"
         perms = 555
       }