redhat: Use NetworkManager to set DHCP hostnames on recent RHEL distros

[mgamal]

Recent versions of RHEL 8 and RHEL 9 (i.e. RHEL8.6/9.1) started using NetworkManager to configure
network intefaces instead of sysconfig files. Configurations are no longer
stored in /etc/sysconfig/ifcfg-{interface}. Setting DHCP hostnames through these files causes provisioning with WALA to fail.

Fix this for setting DHCP hostnames in those RHEL versions.

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[mgamal]

@narrieta @kevinclark19a @ZhidongPeng @nagworld9 @dhivyaganesan can someone please take a look here? The PR is necessary for WALA to function on recent RHEL versions.

Thanks

[nagworld9]

@mgamal Thanks for the PR. Is this happening on custom image where no cloud-init enabled? could you provide steps that you followed to test this fix?

[codecov]

Codecov Report

Merging #2640 (c8e25ec) into develop (4db3b44) will decrease coverage by 0.01%.
The diff coverage is 20.00%.

@@             Coverage Diff             @@
##           develop    #2640      +/-   ##
===========================================
- Coverage    71.96%   71.95%   -0.02%     
===========================================
  Files          103      103              
  Lines        15632    15637       +5     
  Branches      2488     2489       +1     
===========================================
+ Hits         11250    11251       +1     
- Misses        3868     3872       +4     
  Partials       514      514              

Impacted Files	Coverage Δ
azurelinuxagent/common/osutil/redhat.py	50.49% <20.00%> (-1.59%)	⬇️

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[yuxisun1217]

I think it is refer to issue #2593 .

[mgamal]

I think it is refer to issue #2593 .

That's true. RHEL8.6/9.1 use NetworkManager and store configurations per connection instead of using sysconfig files and this PR uses NetworkManager tools to set DHCP hostnames.