Allow configuration of web.noop

[cirocosta]

Feature Request

What challenge are you facing?

When facing a disruption in a Concourse installation, it's useful for operators to have the ability to impede the scheduling while performing maintenance, i.e., being able to leverage the --noop option:

      -n, --noop            Don't actually do any automatic scheduling or checking. [$CONCOURSE_NOOP]

A Modest Proposal

Have the noop flag configurable.

The following can also be handy:

• Concourse version: 5.2.1
• Deployment type (BOSH/Docker/binary): BOSH
• Infrastructure/IaaS: ~
• Browser (if applicable): ~