asn1/asn_moid.c: overhaul do_create.

Original could allocate nid and then bail out on malloc failure. Instead
allocate first *then* attempt to create object.

Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6998)