SqlServerLogin: Error is thrown when SqlLogin is run in Integrated mode

[johlju]

Pull Request (PR) description

• Changes to SqlServerLogin
  • Now when adding a login of type SqlLogin, and the SQL Server login mode
    is set to 'Integrated', an error is correctly thrown
    (issue #1179).

This Pull Request (PR) fixes the following issues

• Fixes SqlServerLogin: When LoginMode is 'Integrated' there is no error thrown #1179

Task list

• Added an entry under the Unreleased section of the change log in the CHANGELOG.md.
  Entry should say what was changed, and how that affects users (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 Resource Testing Guidelines.
• Integration tests added/updated (where possible). See DSC Resource Testing Guidelines.
• New/changed code adheres to DSC Resource Style Guidelines and Best Practices.

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This change is 

[codecov-io]

Codecov Report

Merging #1266 into dev will not change coverage.
The diff coverage is 100%.

@@         Coverage Diff          @@
##            dev   #1266   +/-   ##
====================================
  Coverage    97%     97%           
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  Files        34      34           
  Lines      4197    4197           
====================================
  Hits       4106    4106           
  Misses       91      91

[johlju]

Reviewed 4 of 4 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved