Add test for migration using --on-a-stick command
Add test for migration using --on-a-stick command

When --on-a-stick command is used with a single instance defined it
should migrate the instance to work in a stick  (replace the device
with the one provided in the flag and remove the device in
`external-device`). It just checks that it works by not crashing and
says it's going to do it in the output.

snabbco/snabb,SnabbCo/snabbswitch,SnabbCo/snabbswitch,alexandergall/snabbswitch,dpino/snabbswitch,dpino/snabb,eugeneia/snabb,dpino/snabb,Igalia/snabbswitch,Igalia/snabbswitch,Igalia/snabb,eugeneia/snabb,eugeneia/snabbswitch,dpino/snabbswitch,SnabbCo/snabbswitch,snabbco/snabb,eugeneia/snabbswitch,Igalia/snabbswitch,snabbco/snabb,eugeneia/snabb,eugeneia/snabbswitch,eugeneia/snabbswitch,dpino/snabbswitch,alexandergall/snabbswitch,snabbco/snabb,alexandergall/snabbswitch,SnabbCo/snabbswitch,snabbco/snabb,Igalia/snabb,Igalia/snabbswitch,Igalia/snabb,alexandergall/snabbswitch,dpino/snabbswitch,snabbco/snabb,dpino/snabb,alexandergall/snabbswitch,Igalia/snabb,Igalia/snabb,Igalia/snabb,dpino/snabb,Igalia/snabb,eugeneia/snabb,snabbco/snabb,alexandergall/snabbswitch,alexandergall/snabbswitch,snabbco/snabb,eugeneia/snabb,dpino/snabb,Igalia/snabb,dpino/snabb,eugeneia/snabb,eugeneia/snabb,alexandergall/snabbswitch,eugeneia/snabb,dpino/snabb,Igalia/snabbswitch