files: don't check uninitialized memory in create_link_remap()

Look at this strace output:
107   linkat(45, "", 1017, "./root/git/orig/criu/test/zdtm/live/static/unlink_fstat03.test (deleted)/link_remap.4", AT_EMPTY_PATH) = -1 ENOENT (No such file or director

It's obvious, that we didn't cat the file name.

Here is an error in calculation of offset for the last symbol.
The current version of code sets this offset in strlen(),
but it's actually strlen() - 1.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>