lib/sync: avoid unwanted unlink after download fail

In case we have a mirror failure, unlink_on_fail would remain set,
causing an interrupt in a successive download attempt to be wrongly
unlinked.

This also fixes a memory leak in the url member, as we would allocate
over the previous, unfreed URL.

Signed-off-by: Dave Reisner <dreisner@archlinux.org>

lib/libalpm/sync.c

@@ -896,6 +896,8 @@ static int download_files(alpm_handle_t *handle, alpm_list_t **deltas)
 					if(ret != -1) {
 						break;
 					}
+					free(payload->fileurl);
+					payload->unlink_on_fail = 0;
 				}
 				if(ret == -1) {
 					errors++;