mastodon_db_backup.sh - fix absence of container name

backups/mastodon_db_backup.sh

@@ -21,7 +21,7 @@ backup() {
   rm -f $(readlink -f "$backupdir/$link")
 
   # create new backup file
-  docker exec pg_dumpall -U postgres -c -v | gzip >"$backupdir/$file"
+  docker exec -it "$cname" pg_dumpall -U postgres -c -v | gzip >"$backupdir/$file"
   status=$?
 
   # link the sequence number to it