MINOR: ssl: Destroy ocsp update http_client during cleanup

If a deinit is started while an OCSP update is in progress we might end
up with a dangling http_client instance that should be destroyed
properly.
diff --git a/src/ssl_ocsp.c b/src/ssl_ocsp.c
index 99edfc8..ef624b0 100644
--- a/src/ssl_ocsp.c
+++ b/src/ssl_ocsp.c
@@ -846,6 +846,11 @@
 
 	ssl_sock_free_ocsp(ssl_ocsp_task_ctx.cur_ocsp);
 	ssl_ocsp_task_ctx.cur_ocsp = NULL;
+
+	if (ssl_ocsp_task_ctx.hc) {
+		httpclient_stop_and_destroy(ssl_ocsp_task_ctx.hc);
+		ssl_ocsp_task_ctx.hc = NULL;
+	}
 }
 
 static inline void ssl_ocsp_set_next_update(struct certificate_ocsp *ocsp)