Sync eng/common directory with azure-sdk-tools for PR 3124 (#28158)

* Do not fail remove test resources step when env var is not set.

* Handle empty service directories in remove test resources script

Co-authored-by: Ben Broderick Phillips <bebroder@microsoft.com>

eng/common/TestResources/Remove-TestResources.ps1

@@ -132,11 +132,15 @@ $context = Get-AzContext
 
 if (!$ResourceGroupName) {
     if ($CI) {
+        if (!$ServiceDirectory) {
+            Write-Warning "ServiceDirectory parameter is empty, nothing to remove"
+            exit 0
+        }
         $envVarName = (BuildServiceDirectoryPrefix (GetServiceLeafDirectoryName $ServiceDirectory)) + "RESOURCE_GROUP"
         $ResourceGroupName = [Environment]::GetEnvironmentVariable($envVarName)
         if (!$ResourceGroupName) {
-            Write-Error "Could not find resource group name environment variable '$envVarName'"
-            exit 1
+            Write-Error "Could not find resource group name environment variable '$envVarName'. This is likely due to an earlier failure in the 'Deploy Test Resources' step above."
+            exit 0
         }
     } else {
         if (!$BaseName) {

eng/common/TestResources/SubConfig-Helpers.ps1

@@ -5,7 +5,7 @@ function BuildServiceDirectoryPrefix([string]$serviceName) {
 # If the ServiceDirectory has multiple segments use the last directory name
 # e.g. D:\foo\bar -> bar or foo/bar -> bar
 function GetServiceLeafDirectoryName([string]$serviceDirectory) {
-    return Split-Path -Leaf $serviceDirectory
+    return $serviceDirectory ? (Split-Path -Leaf $serviceDirectory) : ""
 }
 
 function GetUserName() {