Fix ct_test to not assume it's in the source directory

ct_test assumed it's run in the source directory and failed when built
elsewhere.  It still defaults to that, but can be told another story
with the environment variables CT_DIR and CERTS_DIR.

Test recipe updated to match.
Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NEmilia Käsper <emilia@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>

test/recipes/80-test_ct.t

@@ -8,4 +8,3 @@ $ENV{CTLOG_FILE} = srctop_file("test", "ct", "log_list.conf");
 $ENV{CT_DIR} = srctop_file("test", "ct");
 $ENV{CERTS_DIR} = srctop_file("test", "certs");
 simple_test("test_ct", "ct_test", "ct", "ec");
-