Remove replication event from pending when runway is allowed

Consider a replication event not pending anymore *only if* the runway
is free and allowed to run. Removing it too early would result in a
ghost event which isn't officially pending but that will be eventually
run when rescheduled.

Change-Id: Ib0ffa3bec7a6d5d5be56e78a677e8b2133f91e18

src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java b/src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java
index 40f9900..9aab0f6 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/Destination.java
@@ -465,11 +465,11 @@
       if (op.wasCanceled()) {
         return RunwayStatus.canceled();
       }
-      pending.remove(op.getURI());
       PushOne inFlightOp = inFlight.get(op.getURI());
       if (inFlightOp != null) {
         return RunwayStatus.denied(inFlightOp.getId());
       }
+      pending.remove(op.getURI());
       inFlight.put(op.getURI(), op);
     }
     return RunwayStatus.allowed();