add migrator to set head blobs should_announce=0

lbry/extras/daemon/migrator/dbmigrator.py

@@ -37,6 +37,8 @@ def migrate_db(conf, start, end):
             from .migrate13to14 import do_migration
         elif current == 14:
             from .migrate14to15 import do_migration
+        elif current == 15:
+            from .migrate15to16 import do_migration
         else:
             raise Exception(f"DB migration of version {current} to {current+1} is not available")
         try:

lbry/extras/daemon/migrator/migrate15to16.py

@@ -0,0 +1,17 @@
+import os
+import sqlite3
+
+
+def do_migration(conf):
+    db_path = os.path.join(conf.data_dir, "lbrynet.sqlite")
+    connection = sqlite3.connect(db_path)
+    cursor = connection.cursor()
+
+    cursor.executescript("""
+        update blob set should_announce=0
+        where should_announce=1 and 
+        blob.blob_hash in (select stream_blob.blob_hash from stream_blob where position=0);
+    """)
+
+    connection.commit()
+    connection.close()