openssl_stream: fix releasing OpenSSL locks

The OpenSSL library may require multiple locks to work correctly, where
it is the caller's responsibility to initialize and release the locks.
While we correctly initialized up to `n` locks, as determined by
`CRYPTO_num_locks`, we were repeatedly freeing the same mutex in our
shutdown procedure.

Fix the issue by freeing locks at the correct index.

src/openssl_stream.c

@@ -66,7 +66,7 @@ static void shutdown_ssl_locking(void)
 	CRYPTO_set_locking_callback(NULL);
 
 	for (i = 0; i < num_locks; ++i)
-		git_mutex_free(openssl_locks);
+		git_mutex_free(&openssl_locks[i]);
 	git__free(openssl_locks);
 }