uss/snapd: Handle readlink fops on snap view server

Handle readlink fops in case of symlinks on
snap view server

BUG: 1162462
Change-Id: Ia08e9e9c1c61e06132732aa580c5a9fd5e7c449b
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/9102
Reviewed-by: Vijaikumar Mallikarjuna <vmallika@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>