quotad: Remove dead code

client_t is created by server xlator for managing connection related
resources. Quotad doesn't do that. So no need to handle anything related
to it.

Change-Id: I83e6f9e1c57458d60529dc62086bb63642932d49
BUG: 1113403
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/8180
Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>