docs: Clarify docker volume behaviour

list singularity as a community driver

Fixes #5566 .

Fix a case where docker logging process may lock up nomad agent restart.

Looks like we have a case where docker logger is started even through logmon isn't. In such case, the fifo writer blocks indefinitely and because the open operation happens in the main goroutine, nomad agent blocks indefinitely.

This fixes the issue where the fifo open operation happens in goroutine instead of main goroutine.

We should follow up independently to ensure logmon <-> dockerlogger ordering and consider having task recovery happen in non-main goroutine with some sensible timeouts.

Signed-off-by: Eduardo Arango <eduardo@sylabs.io>

Signed-off-by: Eduardo Arango <eduardo@sylabs.io>

vault: fix renewal time

Renewal time was being calculated as 10s+Intn(lease-10s), so the renewal
time could be very rapid or within 1s of the deadline: [10s, lease)

This commit fixes the renewal time by calculating it as:

	(lease/2) +/- 10s

For a lease of 60s this means the renewal will occur in [20s, 40s).

client: simplify kill logic

api: fix migrate stanza initialization

docs: Add docs for nomad-alloc-restart

cli: add support for periodic force evaluation

Add `nomad alloc restart` and `nomad status -verbose`

Merge branch 'website_docs_singularity' of github.com:ArangoGutierrez/nomad into website_docs_singularity

Signed-off-by: Eduardo Arango <eduardo@sylabs.io>

resolves #3251

UI: Make tests faster

vault namespaces: inject VAULT_NAMESPACE alongside VAULT_TOKEN

Signed-off-by: Eduardo Arango <eduardo@sylabs.io>

Refactor scheduler package to enable preemption for batch/service jobs

cli: add `acl token list` command, documentation

docs: fix some incorrect acl policy docs (typos, copy-paste errors)

website: Update hashicorp-middleman container to v0.3.39

Fixes Migrate to be initialized like RescheduleStrategy.

Fixes #5477

Revert accidental merge of pr #5482