Consul lock executes children under a shell, which was previously
undocumented. Document it, and warn against cases where this can cause
children to leak when the lock is lost.
I have made this a dedicated section so it can easily be removed
later when we move to exec
https://github.com/hashicorp/consul/issues/1692
Previously, it would try once "up to" the timeout, but in practice it would
just fall through. This modifies the behavior to block until the timeout has
been reached.
Evan Gilman