Only use environment variables if uid and gid are the same as euid and egid.

This is part of a large change submitted by Markus Friedl <markus@openbsd.org>

crypto/threads/mttest.c

@@ -267,7 +267,8 @@ bad:
 		goto end;
 		}
 
-	if (cipher == NULL) cipher=getenv("SSL_CIPHER");
+	if (cipher == NULL && OPENSSL_issetugid() == 0)
+		cipher=getenv("SSL_CIPHER");
 
 	SSL_load_error_strings();
 	OpenSSL_add_ssl_algorithms();