bug 6643 hwvtep configuration reconcilation

bug 6643 hwvtep configuration reconcilation

Added operational node listener to trigger reconcillation
listens for physical switch node added event and schedules the reconcillation.
trigger transactions for changes in macs and logical switches and vlan bindings
trigger transactions for removal of local ucast and mcast macs aswell
so that to be deleted logical switches will not have any references
cancel the queued reconcilation task if any upon receiving node disconnect event

fixed some npes in mac remove commands
run the logical switch remove command post mac entries remove command as
those logical switches removed logical swithes have to be visible in the
other remove commands

validated the following test cases
1) disconnect the device and push the config (logical switch and remote
macs and vlan bindings ) and connect the device again
2) disconnect the device and delete some confing and connect the device
again

Change-Id: I12d0692e4c8b040f261a9c2cc5cffc05bef96f0d
Signed-off-by: K.V Suneelu Verma <k.v.suneelu.verma@ericsson.com>