Add DbaAgentSchedule tests

[joshcorr]

Type of Change

• Bug fix (non-breaking change, fixes #)
• New feature (non-breaking change, adds functionality)
• Breaking change (effects multiple commands or functionality)
• Ran manual Pester test and has passed (`.\tests\manual.pester.ps1)
• Adding code coverage to existing functionality
• Pester test is included
• If new file reference added for test, has is been added to github.com/sqlcollaborative/appveyor-lab ?
• Nunit test is included
• Documentation
• Build system

Purpose

Include Tests for cmdlets with the noun DbaAgentSchedule which previously had 0 code coverage.

Approach

Created a bunch of schedules to iterate through all options on parameters.

Commands to test

Invoke-Pester .\New-DbaAgentSchedule.Tests.ps1
Invoke-Pester .\Remove-DbaAgentSchedule.Tests.ps1
Invoke-Pester .\Set-DbaAgentSchedule.Tests.ps1

[potatoqualitee]

test failed elsewhere 🍌 💃

[potatoqualitee]

thank you so very very much 🙇