Test-SecretVault does not store sign-in token in env var if timeout exceeded

[DonPwrShellHunt]

Scenario

• Use Test-SecretVault to trigger authentication
• Sign-in token gets put in env variable
• Do stuff - after 30 minutes the token expires
• Use Test-SecretVault to trigger authentication again
• Token is not retrieved & refreshed in env var

# Suggest following syntax for statement 39
$token = & op signin $accountName --raw

[cdhunt]

Relates to #2