vswitchd: In-band rules for Controller are missing after executing force-reload-kmod...

vswitchd: In-band rules for Controller are missing after executing force-reload-kmod command

In current implementation vswitchd adds Controller in-band rules only if
there is a route in kernel routing table that might route traffic to the
Controller. But, when executing force-reload-kmod command, network
configuration (e.g. assigned IP addresses, routes) are flushed away,
hence Controller in-band rules are not added.

This commit fixes this limitation and allows vswitchd to add Controller
in-band rules even if there are no routes in the kernel routing table.

Issue: #8625

Signed-off-by: Ansis Atteka <aatteka@nicira.com>