Add a capability disableSeccomp to disable the seccomp system call filter.

[jschwartzentruber]

This is required to run rr inside a container, as described here: https://github.com/mozilla/rr/wiki/Docker

I haven't been able to run the test locally, mocha says: "pending". I'm hoping it'll be run in CI.

[community-tc-integration]

No Taskcluster jobs started for this pull request

The `allowPullRequests` configuration for this repository (in `.taskcluster.yml` on the
default branch) does not allow starting tasks for this pull request.

[walac]

LGTM, but would you mind adding an worker configuration to disable this feature similar to allowPrivileged ?

[walac]

It took a while but the tasks now run, it feels like disableSeccomp tasks are failing

[walac]

@djmitche another one:

diff --git a/test/dockerworker.js b/test/dockerworker.js
index 8ed1eef8..7ef763d6 100644
--- a/test/dockerworker.js
+++ b/test/dockerworker.js
@@ -64,7 +64,7 @@ class DockerWorker {
           global.asyncDump ? '--require /worker/src/lib/async-dump' : '',
           '/worker/src/bin/worker.js',
           '--host test',
-          '--worker-group', 'random-local-worker',
+          '--worker-group', 'docker-worker',
           '--worker-id', this.workerId,
           '--provisioner-id', this.provisionerId,
           '--worker-type', this.workerType,

[djmitche]

Not my PR, but I pushed that change :)

[walac]

Not my PR, but I pushed that change :)

Ops, I commented in the wrong PR, it actually applies to yours, sorry