SPSearchCrawlerImpactRule: Does throw if Rule does not exist.

[ChristophHannappel]

Pull Request (PR) description

The Ressource threw an error if the Crawler Impact Rule did not exist.

This Pull Request (PR) fixes the following issues

• Fixes SPSearchCrawlerImpactRule: Get-TargetResource throws if Impact Rule does not exist #1444

Task list

• Added an entry to the change log under the Unreleased section of the file CHANGELOG.md.
  Entry should say what was changed and how that affects users (if applicable), and
  reference the issue being resolved (if applicable).
• Resource documentation added/updated in README.md.
• Resource parameter descriptions added/updated in README.md, schema.mof and comment-based
  help.
• Comment-based help added/updated.
• Localization strings added/updated in all localization files as appropriate.
• Examples appropriately added/updated.
• Unit tests added/updated. See DSC Community Testing Guidelines.
• Integration tests added/updated (where possible). See DSC Community Testing Guidelines.
• New/changed code adheres to DSC Community Style Guidelines.

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This change is 

[ChristophHannappel]

I did some changes to the unit tests:

• The Unit Tests used an URI as Parameter Name. But according to the documentation only the Hostname is needed

  Type the name of a site. Do not include the protocol (for example 'http://').

• The Mocked Get-SPEnterpriseSearchSiteHitRule returned the wrong properties
• Fixed some logic errors: Where the test is should exist and does exist - than probes if the Set-SPEnterpriseSearchSiteHitRule gets called and expects an Abenst on the Get Method

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84%. Comparing base (fd20715) to head (9965010).
Report is 6 commits behind head on master.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #1445   +/-   ##
======================================
- Coverage      84%     84%   -1%     
======================================
  Files         145     145           
  Lines       22809   22809           
======================================
- Hits        19246   19244    -2     
- Misses       3563    3565    +2     

Files with missing lines	Coverage Δ
...wlerImpactRule/MSFT_SPSearchCrawlerImpactRule.psm1	92% <100%> (-2%)	⬇️

[ykuijs]

LGTM