files-reg: Eliminate memory leak in open_remap_ghost on errors

xmalloc'ed gf and gf->path are not freed if something failed.
Not a big deal since we're ususally interrupt program execution
on error and do exit, but anyway.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>