storage/posix: Don't unlink .glusterfs-hardlink before linkto check

BUG: 1138385
Change-Id: I90a10ac54123fbd8c7383ddcbd04e8879ae51232
Signed-off-by: Venkatesh Somyajulu <vsomyaju@redhat.com>
Reviewed-on-master: http://review.gluster.org/8559
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: N Balachandran <nbalacha@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/8612