rabbit_vhosts: Don't reconcile vhosts if rabbit is stopped

[Why]
That timer was started during boot and continued regardless if `rabbit`
was running or stopped.

This caused the reconsiliation to crash if the `rabbit` app was stopped
before the it ended because it tried to access the database even though
it was stopped or even reset.

[How]
We just check if `rabbit` is running before running one reconciliation
and scheduling a new one.

Author: dumbbell

deps/rabbit/src/rabbit_vhosts.erl

@@ -51,7 +51,7 @@ boot() ->
 %% See start_processes_for_all/1.
 -spec reconcile() -> 'ok'.
 reconcile() ->
-    case is_reconciliation_enabled() of
+    case rabbit:is_running() andalso is_reconciliation_enabled() of
         false -> ok;
         true  ->
             _ = reconcile_once(),