OCSP: fix memory leak in OCSP_url_svcloc_new method.

Add a few coverage test case.

Fixes #8949

[extended tests]

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/8959)

(cherry picked from commit 5b3accde)