migration_manager: do not pull schema if raft is on

After consistent schema changes, remove schema pulls from gossiper
events if Raft is enabled, and considering Raft upgrade state.

Only disable pull if Raft is fully enabled.

Fixes scylladb#12870

Signed-off-by: Alejo Sanchez <alejo.sanchez@scylladb.com>

Closes scylladb#13695

service/migration_manager.cc

@@ -1215,7 +1215,9 @@ future<column_mapping> get_column_mapping(table_id table_id, table_schema_versio
 }
 
 future<> migration_manager::on_join(gms::inet_address endpoint, gms::endpoint_state ep_state) {
-    schedule_schema_pull(endpoint, ep_state);
+    if (!_group0_client.using_raft()) {
+        schedule_schema_pull(endpoint, ep_state);
+    }
     return make_ready_future();
 }
 
@@ -1227,14 +1229,18 @@ future<> migration_manager::on_change(gms::inet_address endpoint, gms::applicati
             return make_ready_future();
         }
         if (_storage_proxy.get_token_metadata_ptr()->is_normal_token_owner(endpoint)) {
-            schedule_schema_pull(endpoint, *ep_state);
+            if (!_group0_client.using_raft()) {
+                schedule_schema_pull(endpoint, *ep_state);
+            }
         }
     }
     return make_ready_future();
 }
 
 future<> migration_manager::on_alive(gms::inet_address endpoint, gms::endpoint_state state) {
-    schedule_schema_pull(endpoint, state);
+    if (!_group0_client.using_raft()) {
+        schedule_schema_pull(endpoint, state);
+    }
     return make_ready_future();
 }