Reduce scope of VS-DP mapping table

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Log when VS-DP mappings are updated

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Indicate the success of processing IPC messages

IPCMessageProcessor.process() is expected to return a boolean value
indicating whether the processing of a message is successful. This patch
makes process() return false for unsupported message types.

Signed-off-by: Joe Stringer <joe@wand.net.nz>
Improve logging messages in packet_in handler

Signed-off-by: Joe Stringer <joe@wand.net.nz>