Unable to change mtu value on compute mgmt interface

[George Postolache]

Brief Description
-----------------
unable to change the mtu value in the mgmt interfaces on the compute nodes
Should i be able to change mtu value for mgmt interface?

Severity
--------
minor

Steps to Reproduce
------------------
system host-lock controller-1
system host-if-modify -m 1420 controller-1 <mgmt>
system host-unlock controller-1
system host-swact controller-0
# connect to controller-1
system host-lock controller-0
system host-if-modify -m 1420 controller-0 <mgmt>
system host-unlock controller-0
# 270.001 alarm is present after unlocking controller-0
system host-lock compute-0 now fails (vim_progress_status | services-disable-failed)

Expected Behavior
------------------
Should be able to lock compute-0/compute-1 to change the value

Actual Behavior
----------------
locking compute-0/compute-1 fails

Reproducibility
---------------
always

System Configuration
--------------------
Multi-node system

Branch/Pull Time/Commit
-----------------------
BUILD_ID="20200616T000950Z"
BUILD_DATE="2020-06-16 00:09:50 +0000"

Last Pass
---------

Timestamp/Logs
--------------
https://files.starlingx.kube.cengn.ca/launchpad/1883738

Test Activity
-------------
Regression Testing

Workaround
----------
Describe workaround if available

[Ghada Khalil (gkhalil)]

Based on the discussion in the stx networking team on 2020-07-09, we believe this is procedural.
For the cluster-host, the mtu cannot be changed as the value from the network resource is always used.

[Steven Webster (swebster-wr)]

Note: from a quick look at the database dump in the logs, it looks like the cluster-host network is shared with the management on the same interface. It sounds like we may need a semantic check or something similar to prevent the modify or unlock in this case. Needs further investigation

[Ghada Khalil (gkhalil)]

Marking as low priority for now as this is not a typical use-case.