Switch to a single tunnel for all mappings, this removes the limitations
on how many mappings each tunnel can handle, and therefore how many Fan
slices each local address may hold.

NOTE: This introduces a new kernel netlink interface which needs updated
iproute2 support.

BugLink: http://bugs.launchpad.net/bugs/1470091Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

Conflicts:
	include/net/ip_tunnels.h