issue #223: correctly detect if reversible data have to be removed after hived restart

• now fork event is added only when hived wills end notification, no artificial event during 'hive.connect'
• hive.connect is always executed before on_reindex notification, before data are marked as dirty

src/hive_fork_manager/hived_api.sql

@@ -27,6 +27,10 @@ $BODY$
 DECLARE
     __fork_id BIGINT;
 BEGIN
+    IF (SELECT COUNT(*) FROM hive.fork ) > 0 THEN
+        RETURN;
+    END IF;
+
     INSERT INTO hive.fork(block_num, time_of_fork)
     VALUES( _block_num_before_fork, LOCALTIMESTAMP );
 
@@ -338,7 +342,7 @@ AS
 $BODY$
 BEGIN
     PERFORM hive.remove_inconsistent_irreversible_data();
-    IF _remove_reversible OR _block_num = 0 THEN --_block_num = 0 to ensure that at least 1 fork exists
+    IF _block_num = 0 THEN --_block_num = 0 to ensure that at least 1 fork exists
         PERFORM hive.back_from_fork( _block_num );
     END IF;
     INSERT INTO hive.hived_connections( block_num, git_sha, time )