BUG/MINOR: checks: Only use ssl_sock_is_ssl() if compiled with SSL support

ssl_sock_is_ssl() only exists if HAProxy is complied with SSL support.

No backport needed.
diff --git a/src/checks.c b/src/checks.c
index efc9ce2..414c39e 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -2511,8 +2511,11 @@
 		}
 		else if (rule->action == TCPCHK_ACT_CONNECT) {
 			const char *msg = ((rule->connect.options & TCPCHK_OPT_IMPLICIT) ? NULL : "(tcp-check)");
-			enum healthcheck_status status = ((conn && ssl_sock_is_ssl(conn)) ? HCHK_STATUS_L6OK : HCHK_STATUS_L4OK);
-
+			enum healthcheck_status status = HCHK_STATUS_L4OK;
+#ifdef USE_OPENSSL
+			if (conn && ssl_sock_is_ssl(conn))
+				status = HCHK_STATUS_L6OK;
+#endif
 			set_server_check_status(check, status, msg);
 		}
 	}