LU-8056 llite: inode_operations interface changed in 4.5

LU-8056 llite: inode_operations interface changed in 4.5

Linux kernel 4.5 replaced follow_link() with get_link()
while put_link() is removed.
This patch handles the API change.

Linux-commit:6b2553918d8b4e6de9853fd6315bec7271a2e592
Linux-commit:fceef393a538134f03b778c5d2519e670269342f

Signed-off-by: Li Dongyang <dongyang.li@anu.edu.au>
Change-Id: Ia9b8c9b855ed5ab7a428a370074b8801e34d3f99
Reviewed-on: http://review.whamcloud.com/20224
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>