MT#61408 Don't fail if there is no revisions to delete

This is rollback case if during the upgrade there is no
not_replicated sql scripts.
In 1st run of 'ngcp-update-db-schema --downgrade-release' deletes all
the records will be deleted on sp1. So the next run on sp2 finds no
records to delete and it's ok.
So don't fail on this case.

Change-Id: Ifcdd6cb369eaa0da0167c50023e5502e06aa3a8a

(cherry picked from commit 3143cc8e60)
Change-Id: I25a0b4d1a3449830de568c17ced5b0633c7e1bb8

ngcp-update-db-schema

@@ -935,13 +935,13 @@ def get_db_schema() -> DBSchema:
 
     if config.mode == 'down' and not db_schema:
         if config.downgrade_release:
-            error(c_str(f"""
-                could not find entries in db_schema \
+            log(c_str(f"""
+                could not find entries in db_schema
                 table matching release '{config.downgrade_release}'
                 """))
         else:
-            error('could not find entries in db_schema')
-        shutdown(1)
+            log('could not find entries in db_schema')
+        shutdown(0)
 
     return db_schema