AzureDevOpsDsc: Increase unit test, code coverage

[SphenicPaul]

Details of the scenario you tried and the problem that is occurring

Test coverage threshold in the build.yml file is currently set to 40 (%) to allow initial builds to execute/succeed - Although a number of classes within the unit tests are covered, Pester is not recognising the coverage.

This needs investigating and may require a refactoring of tests and/or classes (also note #10 relating to classes within the module).

Ideally, attempt to set code coverage threshold to 100% or 95%.

[johlju]

Coverage threshold can be set to 85%, but if the actual code coverage is higher than that it's better.