stx-metal devstack plugin file access permission issue

[Yi Wang]

Title
-----
stx-metal devstack code has permission issue to access /etc/hosts

Brief Description
-----------------
stx-metal devstack plugin failed to modify /etc/hosts due to lack of permission

Severity
--------
Provide the severity of the defect.
minor

Steps to Reproduce
------------------
launch devstack with stx-metal plugin enabled

Expected Behavior
------------------
stack.sh failed due to errors happened in stx-metal plugin code

Actual Behavior
----------------
stack.sh successfully end

Reproducibility
---------------
Reproducible

System Configuration
--------------------
one node

Branch/Pull Time/Commit
-----------------------
the latest code

Timestamp/Logs
--------------
n/a

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/637708

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/637708
Committed: https://git.openstack.org/cgit/openstack/stx-metal/commit/?id=ab3f2385e84cf015760d34317a6085008563901c
Submitter: Zuul
Branch: master

commit ab3f2385e84cf015760d34317a6085008563901c
Author: Yi Wang <email address hidden>
Date: Wed Feb 20 14:49:01 2019 +0800

    fix a devstack plugin bug

    devstack default user stack may not have permission to modify system
    file /etc/hosts. use sudo to make sure the modification is done.

    Change-Id: Iabe47cae88da9d70a1f7788c1847d99856963713
    Closes-Bug: 1816520
    Signed-off-by: Yi Wang <email address hidden>

[Ghada Khalil (gkhalil)]

Adding stx.2019.05 tag as this fix was merged for that release