LU-16060 osd-ldiskfs: copy nul byte terminator in writelink

LU-16060 osd-ldiskfs: copy nul byte terminator in writelink

memcpy() call in osd_ldiskfs_writelink() doesn't copy the nul
terminator byte from the source buffer, leaving the space
after target link name uninialized which is ok for the kernel
code and debugfs but not e2fsck.

HPE-bug-id: LUS-11103

Signed-off-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Change-Id: I914f2c78e1a6571bf360a23b0ede8c70502bf0df
Reviewed-on: https://review.whamcloud.com/48092
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Reviewed-by: Andrew Perepechko <andrew.perepechko@hpe.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>