VCL: refactor session close / disconnect.
VCL: refactor session close / disconnect.

Change-Id: Ib0797faaa3f21c7577330bb8d0e801d43e01110e
Signed-off-by: Dave Wallace <0ed937c0e4b2f09f7bc24acf16cee52b8a199d5f@gmail.com>

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