Fixes setting MTU on adapters to be disabled
Fixes setting MTU on adapters to be disabled

Fixes the issue by setting the MTU before disabling an adapter.

Change-Id: I1590074e165fbd5214812b4f247702cd6bb9a972
Closes-Bug: #1800063

openstack/cloudbase-init,ader1990/cloudbase-init,stackforge/cloudbase-init,alexpilotti/cloudbase-init