When using the option --storagekey for the prepdocs script the key mi…

…ght (Azure-Samples#866)

contain `==` base64 padding at the end. This will fail to succesfully
login because the script just removes the `=` signs during the split
action. Copied the version from the app/start.ps1 which is better suited here.

Co-authored-by: Pamela Fox <pamelafox@microsoft.com>

scripts/loadenv.ps1

@@ -1,16 +1,12 @@
 Write-Host "Loading azd .env file from current environment"
-$output = azd env get-values
-foreach ($line in $output) {
-    if (!$line.Contains('=')) {
-    continue
+foreach ($line in (& azd env get-values)) {
+    if ($line -match "([^=]+)=(.*)") {
+        $key = $matches[1]
+        $value = $matches[2] -replace '^"|"$'
+	    [Environment]::SetEnvironmentVariable($key, $value)
     }
-
-    $name, $value = $line.Split("=")
-    $value = $value -replace '^\"|\"$'
-    [Environment]::SetEnvironmentVariable($name, $value)
 }
 
-
 $pythonCmd = Get-Command python -ErrorAction SilentlyContinue
 if (-not $pythonCmd) {
   # fallback to python3 if python not found