ossl_property_list_to_string: handle quoted strings

ossl_property_list_to_string() didn't quote strings correctly which
could result in a generated property string being unparsable.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22182)