Update TrustedHosts setting with ToString method (#531)

We noticed a cast exception in our tests ->
Cannot convert 'System.Object[]' to the type 'System.String' required by
the parameter. Specified method is not supported.

# Change type
- [x] Bug fix (non-breaking change)

# Checklist:
- [x] My code follows the style and contribution guidelines of this
project.
- [x] I have tested and validated my code changes.

Author: adfema

src/modules/SdnDiag.Utilities.psm1

@@ -1897,7 +1897,7 @@ function New-PSRemotingSession {
                     $trustedHosts = Get-Item -Path "WSMan:\localhost\client\TrustedHosts"
                     if ($trustedHosts.Value -notlike "*$objectName*" -and $trustedHosts.Value -ne "*") {
                         "Adding {0} to {1}" -f $objectName, $trustedHosts.PSPath | Trace-Output
-                        Set-Item -Path "WSMan:\localhost\client\TrustedHosts" -Value $objectName -Concatenate
+                        Set-Item -Path "WSMan:\localhost\client\TrustedHosts" -Value $objectName.ToString() -Concatenate -Force
                     }
                 }
                 catch {