shared/validate/validate: Increases max MTU to 16384 to support super jumbo packets
shared/validate/validate: Increases max MTU to 16384 to support super jumbo packets

Fixes https://github.com/lxc/lxd/issues/7972

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

lxc/lxd,stgraber/lxd,atxwebs/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,atxwebs/lxd,stgraber/lxd,hallyn/lxd,atxwebs/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd,atxwebs/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,lxc/lxd