Cannot set MTU to 1500

[Ian Pilcher]

Currently os-net-config uses 1500 as the default (or not specifically set) value for the MTU, and it doesn't write the MTU to the network configuration if it is set to 1500. There are times, however, when it is desireable to specifically set the MTU to 1500 -- most commonly when one doesn't want a particular VLAN interface to inherit a large MTU from its physical device.

The attached patch changes to using -1 as the "not specifically set" value so that an MTU of 1500 can be specifically set.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/275953

[Ben Nemec (bnemec)]

Marking invalid for tripleo as this is really an os-net-config bug.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/275953
Committed: https://git.openstack.org/cgit/openstack/os-net-config/commit/?id=047294481fc4a2161e8ef637ad3a2706b85bce26
Submitter: Jenkins
Branch: master

commit 047294481fc4a2161e8ef637ad3a2706b85bce26
Author: Ian Pilcher <email address hidden>
Date: Wed Feb 3 16:06:56 2016 -0600

    Allow setting MTU to 1500

    There are times when it is desirable to set the MTU of an
    "interface" to 1500 -- when the external network and the storage
    network are different VLANs on the same physical interface, for
    example.

    Change-Id: Ic5ea6ad05118fd57c26c898a460c19969de4109d
    Closes-Bug: #1539821