Have step-down request forward.

Unlike seal, this command has no meaning other than on the active node,
so when issuing it the expected behavior would be for whichever node is
currently active to step down.

CHANGELOG.md

@@ -1,5 +1,10 @@
 ## Next (Unreleased)
 
+DEPRECATIONS/CHANGES:
+
+ * Step-Down is Forwarded: When a step-down is issued against a non-active node
+   in an HA cluster, it will now forward the request to the active node.
+
 IMPROVEMENTS:
 
  * plugins/databases: Add MongoDB as an internal database plugin. [GH-2698]

http/handler.go

@@ -46,7 +46,7 @@ func Handler(core *vault.Core) http.Handler {
 	mux.Handle("/v1/sys/init", handleSysInit(core))
 	mux.Handle("/v1/sys/seal-status", handleSysSealStatus(core))
 	mux.Handle("/v1/sys/seal", handleSysSeal(core))
-	mux.Handle("/v1/sys/step-down", handleSysStepDown(core))
+	mux.Handle("/v1/sys/step-down", handleRequestForwarding(core, handleSysStepDown(core)))
 	mux.Handle("/v1/sys/unseal", handleSysUnseal(core))
 	mux.Handle("/v1/sys/renew", handleRequestForwarding(core, handleLogical(core, false, nil)))
 	mux.Handle("/v1/sys/renew/", handleRequestForwarding(core, handleLogical(core, false, nil)))