MDEV-14132 : fix posix_fallocate() calls to workaround some (ancient) Linux bugs

With this patch, parameters passed to posix_fallocate() will be
the same as they were prior to refactoring in  commit b731a5bc

In particular, 'offset' parameter for posix_fallocate is again current_file_size
and 'length' is new_file_size - current_file_size.

This seems to fix crashes on ancient Linux (kernel 2.6).

storage/innobase/os/os0file.cc

@@ -5381,7 +5381,8 @@ os_file_set_size(
 # ifdef HAVE_POSIX_FALLOCATE
 	int err;
 	do {
-		err = posix_fallocate(file, 0, size);
+		os_offset_t current_size = os_file_get_size(file);
+		err = posix_fallocate(file, current_size, size - current_size);
 	} while (err == EINTR
 		 && srv_shutdown_state == SRV_SHUTDOWN_NONE);