Update hostname setting for SUSE distros

[rjschwei]

Description

Current versions of openSUSE and SLES are systemd based. Use hostnamectl to set the hostname and make sure it is properly propagated through the system.

Issue #
The hostname setting may not be properly propagated in the running system using the "hostname" command.

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This change is 

[codecov]

Codecov Report

Merging #1832 into develop will decrease coverage by 0.33%.
The diff coverage is 4.00%.

@@             Coverage Diff             @@
##           develop    #1832      +/-   ##
===========================================
- Coverage    69.45%   69.12%   -0.34%     
===========================================
  Files           82       82              
  Lines        11469    11511      +42     
  Branches      1619     1619              
===========================================
- Hits          7966     7957       -9     
- Misses        3166     3217      +51     
  Partials       337      337              

Impacted Files	Coverage Δ
azurelinuxagent/common/osutil/suse.py	32.11% <4.00%> (-33.57%)	⬇️

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[pgombar]

Travis run is green: https://travis-ci.org/github/Azure/WALinuxAgent/builds/666506710
Internal end-to-end automation is passing, @narrieta can you add your review?

[pgombar]

Hi @rjschwei I was running end-to-end automation for this change and it seems that the hostname in SUSE12 SP5 keeps flip-flopping between localhost and whatever the hostname is set to during provisioning. This happens when either hostname or hostnamectl commands are used to set the hostname during provisioning.

2020/04/22 06:21:06.863525 INFO ExtHandler EnvMonitor: Detected hostname change: localhost-> edpt9hdky6
2020/04/22 06:21:06.873529 INFO ExtHandler Examine /proc/net/route for primary interface
2020/04/22 06:21:06.877988 INFO ExtHandler Primary interface is [eth0]
2020/04/22 06:21:31.683811 INFO ExtHandler EnvMonitor: Detected hostname change: edpt9hdky6-> localhost

We are not seeing this behavior in other images. I did a little bit of research and the hostname change remains persistent if I tell DHCP to not change the hostname like:
sed --in-place 's/DHCLIENT_SET_HOSTNAME="yes"/DHCLIENT_SET_HOSTNAME="no"/' /etc/sysconfig/network/dhcp

Is this behavior expected? cc @trstringer who might have more context on this from the provisioning side.

[rjschwei]

@pgombar the hostname keeps flipping because of a configuration error in our images where we have DHCLIENT_SET_HOSTNAME=yes in /etc/sysconfig/network/dhcp instead of DHCLIENT_SET_HOSTNAME=no.

The issue has been fixed and the next image refresh cycle will have the updated value. It is unknown why this has never been a problem in the past, best guess is that a change in wicked triggered this to show up.

[pgombar]

@pgombar the hostname keeps flipping because of a configuration error in our images where we have DHCLIENT_SET_HOSTNAME=yes in /etc/sysconfig/network/dhcp instead of DHCLIENT_SET_HOSTNAME=no.

The issue has been fixed and the next image refresh cycle will have the updated value. It is unknown why this has never been a problem in the past, best guess is that a change in wicked triggered this to show up.

Thanks for confirming!

Also, thank you for changing all of the calls in suse.py. I was expecting you to change just the method you were touching in this PR.

However, we want to keep the current behaviour of swallowing exceptions and not logging to agent log. Since we want to merge this change as soon as possible, I have updated the PR to expedite the review.

[larohra]

LGTM

[pgombar]

End-to-end automation OK.

[pgombar]

@rjschwei merged, thanks for your contribution!

[rjschwei]

Thanks for cleaning up after me while I was pulled away chasing other stuff.