Fix severity levels in duplicate alert tests and ensure error handling is consistent

Author: johlju

tests/Integration/Commands/New-SqlDscAgentAlert.Integration.Tests.ps1

@@ -117,15 +117,15 @@ END
 
     It 'Should throw error when alert already exists' {
         # First create the alert
-        $script:sqlServerObject | New-SqlDscAgentAlert -Name 'IntegrationTest_DuplicateAlert' -Severity 16 -ErrorAction Stop
+        $script:sqlServerObject | New-SqlDscAgentAlert -Name 'IntegrationTest_DuplicateAlert' -Severity 15 -ErrorAction Stop
 
         # Try to create it again - should throw
-        { $script:sqlServerObject | New-SqlDscAgentAlert -Name 'IntegrationTest_DuplicateAlert' -Severity 14 } |
+        { $script:sqlServerObject | New-SqlDscAgentAlert -Name 'IntegrationTest_DuplicateAlert' -Severity 14 -ErrorAction Stop } |
             Should -Throw
     }
 
     It 'Should throw error when both Severity and MessageId are specified' {
-        { $script:sqlServerObject | New-SqlDscAgentAlert -Name 'IntegrationTest_InvalidAlert' -Severity 16 -MessageId 50001 } |
+        { $script:sqlServerObject | New-SqlDscAgentAlert -Name 'IntegrationTest_InvalidAlert' -Severity 16 -MessageId 50001 -ErrorAction Stop } |
             Should -Throw
     }
 }