don't try adn connect to couch until we manage to check if there is a last_seq

plugins/river/couchdb/src/main/java/org/elasticsearch/river/couchdb/CouchdbRiver.java

@@ -251,6 +251,7 @@ public class CouchdbRiver extends AbstractRiverComponent implements River {
                     logger.warn("failed to get last_seq, throttling....", e);
                     try {
                         Thread.sleep(5000);
+                        continue;
                     } catch (InterruptedException e1) {
                         if (closed) {
                             return;