This endpoint causes the node it's hit to step down from active duty.
It's a noop if the node isn't active or not running in HA mode. The node
will wait one second before attempting to reacquire the lock, to give
other nodes a chance to grab it.
Fixes#1093
This commit splits ACL policies into more fine-grained capabilities.
This both drastically simplifies the checking code and makes it possible
to support needed workflows that are not possible with the previous
method. It is backwards compatible; policies containing a "policy"
string are simply converted to a set of capabilities matching previous
behavior.
Fixes#724 (and others).
