xSQLServerAlwaysOnService: IsHadrEnabled is cast to [System.Boolean]

[johlju]

Pull Request (PR) description

• Changes to xSQLServerAlwaysOnService
  • Casting the result of the property IsHadrEnabled to [System.Boolean] so that $null is never returned,
    which resulted in an exception (issue xSQLServerAlwaysOnService: Returns IsHadrEnabled -eq $null  #763).

This Pull Request (PR) fixes the following issues:
Fixes #763

Task list:

• Change details added to Unreleased section of CHANGELOG.md?
• Added/updated documentation, comment-based help and descriptions in .schema.mof files where appropriate?
• Examples appropriately updated?
• New/changed code adheres to Style Guidelines?
• Unit and (optional) Integration tests created/updated where possible?

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This change is 

[codecov-io]

Codecov Report

Merging #768 into dev will decrease coverage by <1%.
The diff coverage is 100%.

@@         Coverage Diff         @@
##            dev   #768   +/-   ##
===================================
- Coverage    97%    97%   -1%     
===================================
  Files        30     30           
  Lines      3250   3245    -5     
===================================
- Hits       3165   3160    -5     
  Misses       85     85

[johlju]

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Reviewed 3 of 3 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved.

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