Use the new setter for CurrentTimeCallback in bssl_shim.

Change-Id: I0aaf9d926a81c3a10e70ae3ae6605d4643419f89
Reviewed-on: https://boringssl-review.googlesource.com/8210
Reviewed-by: Taylor Brandstetter <deadbeef@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

ssl/test/bssl_shim.cc

diff --git a/ssl/test/bssl_shim.cc b/ssl/test/bssl_shim.cc
index eadc27d..936efbf 100644
--- a/ssl/test/bssl_shim.cc
+++ b/ssl/test/bssl_shim.cc
@@ -830,7 +830,7 @@
   SSL_CTX_enable_tls_channel_id(ssl_ctx.get());
   SSL_CTX_set_channel_id_cb(ssl_ctx.get(), ChannelIdCallback);
 
-  ssl_ctx->current_time_cb = CurrentTimeCallback;
+  SSL_CTX_set_current_time_cb(ssl_ctx.get(), CurrentTimeCallback);
 
   SSL_CTX_set_info_callback(ssl_ctx.get(), InfoCallback);
   SSL_CTX_sess_set_new_cb(ssl_ctx.get(), NewSessionCallback);