store: Guard against a race when remapping shards

Author: lutter

store/postgres/src/connection_pool.rs

@@ -1440,10 +1440,16 @@ impl PoolCoordinator {
         // version. Since dropping and recreating the foreign table
         // definitions can slow the startup of other nodes down because of
         // locking, we try to only do this when it is actually needed
-        for server in self.servers.iter() {
-            if pool.needs_remap(server)? {
-                pool.remap(server)?;
-            }
+        {
+            let mut conn = pool.get()?;
+            with_migration_lock(&mut conn, |_| {
+                for server in self.servers.iter() {
+                    if pool.needs_remap(server)? {
+                        pool.remap(server)?;
+                    }
+                }
+                Ok(())
+            })?;
         }
 
         // pool had schema changes, refresh the import from pool into all