Fix 50x errors while loading page links (Azure#19301)

We have hit a few 50x errors while pulling a page to get
links and that has caused the rest of the link checking to
terminate early. To fix that we switching to LogError which will
output an error in devops instead of Write-Error which terminates
immediately. We also add some retry count to the page retrieval
and cache file retrieval to help with these transitent 50x issues.

Co-authored-by: Wes Haggard <Wes.Haggard@microsoft.com>

Author: azure-sdk

eng/common/scripts/Verify-Links.ps1

@@ -43,7 +43,7 @@
 
   .PARAMETER outputCacheFile
   Path to a file that the script will output all the validated links after running all checks.
-  
+
   .PARAMETER requestTimeoutSec
   The number of seconds before we timeout when sending an individual web request. Default is 15 seconds.
 
@@ -332,7 +332,7 @@ function GetLinks([System.Uri]$pageUri)
 {
   if ($pageUri.Scheme.StartsWith("http")) {
     try {
-      $response = Invoke-WebRequest -Uri $pageUri -UserAgent $userAgent -TimeoutSec $requestTimeoutSec
+      $response = Invoke-WebRequest -Uri $pageUri -UserAgent $userAgent -TimeoutSec $requestTimeoutSec -MaximumRetryCount 3
       $content = $response.Content
 
       if ($pageUri.ToString().EndsWith(".md")) {
@@ -341,7 +341,7 @@ function GetLinks([System.Uri]$pageUri)
     }
     catch {
       $statusCode = $_.Exception.Response.StatusCode.value__
-      Write-Error "Invalid page [$statusCode] $pageUri"
+      LogError "Invalid page [$statusCode] $pageUri"
     }
   }
   elseif ($pageUri.IsFile -and (Test-Path $pageUri.LocalPath)) {
@@ -363,7 +363,7 @@ function GetLinks([System.Uri]$pageUri)
     }
   }
   else {
-    Write-Error "Don't know how to process uri $pageUri"
+    LogError "Don't know how to process uri $pageUri"
   }
 
   $links = ParseLinks $pageUri $content
@@ -396,12 +396,12 @@ if ($inputCacheFile)
   $cacheContent = ""
   if ($inputCacheFile.StartsWith("http")) {
     try {
-      $response = Invoke-WebRequest -Uri $inputCacheFile -TimeoutSec $requestTimeoutSec
+      $response = Invoke-WebRequest -Uri $inputCacheFile -TimeoutSec $requestTimeoutSec -MaximumRetryCount 3
       $cacheContent = $response.Content
     }
     catch {
       $statusCode = $_.Exception.Response.StatusCode.value__
-      Write-Error "Failed to read cache file from  page [$statusCode] $inputCacheFile"
+      LogError "Failed to read cache file from  page [$statusCode] $inputCacheFile"
     }
   }
   elseif (Test-Path $inputCacheFile) {