Fixes bug 2285: MTU Issue

There is a bug in microk8s 1.26.7 where calico will not be
created with the correct MTU:

https://github.com/canonical/microk8s/issues/4142



This patch adds a workaround.

Change-Id: I164e612c03a70e9417b6f736b71f71b8050fddbc
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>