Added the wiki link for steps to be done for upgrade to 3.6.1

Change-Id: Ib7cfc4ef7a8c874ddc8d76c8d2f2493ceec9f6b1
Signed-off-by: Lalatendu Mohanty <lmohanty@redhat.com>
Reviewed-on: http://review.gluster.org/9092
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Niels de Vos <ndevos@redhat.com>
Reviewed-by: Humble Devassy Chirammal <humble.devassy@gmail.com>