session: fix app index in unbind
session: fix app index in unbind

Change-Id: Iff1a665b6cf9ca2def0fcdacf02d7f8c579c0f4e
Signed-off-by: Florin Coras <c9715e5cdf0718c2e9b10678757dfb027875eba2@cisco.com>

vpp-dev/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,vpp-dev/vpp,vpp-dev/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,vpp-dev/vpp,vpp-dev/vpp,chrisy/vpp,vpp-dev/vpp