cs_network_offering: add tags support

[resmo]

closes #77

/cc @div8cn you may want to give it a shot.

[codecov]

Codecov Report

Merging #82 (ede119c) into master (f83d456) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #82      +/-   ##
==========================================
+ Coverage   84.23%   84.25%   +0.01%     
==========================================
  Files          56       56              
  Lines        5590     5597       +7     
  Branches     1256     1255       -1     
==========================================
+ Hits         4709     4716       +7     
+ Misses        446      445       -1     
- Partials      435      436       +1     

Impacted Files	Coverage Δ
plugins/module_utils/cloudstack.py	71.82% <ø> (-0.13%)	⬇️
plugins/modules/cs_network_offering.py	88.17% <100.00%> (+1.26%)	⬆️
plugins/modules/cs_disk_offering.py	94.28% <0.00%> (-2.86%)	⬇️
plugins/modules/cs_service_offering.py	93.24% <0.00%> (-1.36%)	⬇️
plugins/modules/cs_instance.py	71.52% <0.00%> (+0.68%)	⬆️

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[resmo]

Test fails if adding tags to the tests with

Unable to find physical network in zone id=3

However, if i only run this test with tags isolated, test passes. I assume the failing is related to another test. That is why I will merge it in as is nevertheless.