fcntl/fcntl16: close fd before unlink

This testcase fails on NFS but doesn't remove its
working directory on exit (NFS silly rename):

TWARN  :  tst_rmdir: rmobj(/mnt/fcn1GHJ8g) failed: unlink(/mnt/fcn1GHJ8g/.nfs0000000000000c4200000001) failed; errno=16: Device or resource busy

Fixed.

Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
Acked-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>