dbtoyaml: fix RuntimeError when using -n option
dbtoyaml: fix RuntimeError when using -n option

RuntimeError: dictionary changed size during iteration
Signed-off-by: Philippe Pepiot <e888d2bd6f13f82caa51a37c03d034c76f661ba3@philpep.org>

perseas/Pyrseas,reedstrm/Pyrseas,dvarrazzo/Pyrseas