SLING-12289 - Only store status if it does not yet exist (#140)

diff --git a/src/main/java/org/apache/sling/distribution/journal/impl/precondition/PackageStatusWatcher.java b/src/main/java/org/apache/sling/distribution/journal/impl/precondition/PackageStatusWatcher.java
index 89eee8f..936cb84 100644
--- a/src/main/java/org/apache/sling/distribution/journal/impl/precondition/PackageStatusWatcher.java
+++ b/src/main/java/org/apache/sling/distribution/journal/impl/precondition/PackageStatusWatcher.java
@@ -91,8 +91,7 @@
 
     private void handle(MessageInfo info, PackageStatusMessage pkgStatusMsg) {
         long pkgOffset = pkgStatusMsg.getOffset();
-        // TODO: check revision
         Map<Long, Status> agentStatus = getAgentStatus(pkgStatusMsg.getSubAgentName());
-        agentStatus.put(pkgOffset, pkgStatusMsg.getStatus());
+        agentStatus.computeIfAbsent(pkgOffset, offset -> pkgStatusMsg.getStatus());
     }
 }