Changed status of ConcurrentSnapshotException from 5xx -> 429(Too_Man…

…y_Requests).

Signed-off-by: Mani <singh.mani1231@gmail.com>

server/src/main/java/org/opensearch/snapshots/ConcurrentSnapshotExecutionException.java

@@ -58,6 +58,6 @@ public ConcurrentSnapshotExecutionException(StreamInput in) throws IOException {
 
     @Override
     public RestStatus status() {
-        return RestStatus.SERVICE_UNAVAILABLE;
+        return RestStatus.TOO_MANY_REQUESTS;
     }
 }