Extend the BIO callback tests to check the return value semantics

Check that different return values passed to the BIO callback are
correctly handled.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7344)

(cherry picked from commit 52d78cc5ebc1d4fc021cabbcb09f4efb4c6ae82d)