doc: Update bug for replace-brick problems.

Change-Id: I372568d86fe1b043504dd189853e156b2e210b6e
BUG: 825906
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/5579
Reviewed-by: Anand Avati <avati@redhat.com>