Kubespan creates package size more than MTU external interface size.
This PR adds capabilities to change MTU size through machine config.
And sets MTU of the default kubespan route.
Signed-off-by: Serge Logvinov <serge.logvinov@sinextra.dev>
Signed-off-by: Andrey Smirnov <andrey.smirnov@talos-systems.com>