Deploy LinuxDiagnostics using ARM calculated SAS fails

I am unable to deploy the LinuxDiagnotics extension using ARM templates because the SAS token generated by the `listAccountSas()` function in ARM generates expiry date stamps in a format that MdsTime does not support.

My `/var/log/azure/Microsoft.Azure.Diagnostics.LinuxDiagnostic/3.0.113/extension.log` contains the following (note the factional part of the datestamp):

```
2018/09/25 16:09:14 Parse reported these messages:
2018/09/25 16:09:14 /var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic
-3.0.113/xmlCfg.xml(3) Error: Storage credential validation for table storage fa
iled: MdsTime(): expected: RFC3339 date; Actual: decoded='2020-09-19T03:23:47.00
00000Z', original: '2020-09-19T03%3A23%3A47.0000000Z'
```

The simplified ARM template that generates the token is the following,

```
{
"$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"requestContent": {
"type": "object",
"defaultValue": {
"signedServices": "b",
"signedResourceType": "c",
"signedPermission": "r",
"signedExpiry": "2020-09-19T03:23:47Z",
"signedResourceTypes": "s"
}
}
},
"outputs": {
"accountSAS": {
"type": "object",
"value": "[listAccountSas(resourceId('Microsoft.Storage/storageAccounts', 'mystorage'), '2018-02-01', parameters('requestContent'))]"
}
}
}
```

MdsTime parses the timestamp on the following line,

[/Diagnostic/mdsd/mdsdutil/MdsTime.cc](https://github.com/Azure/azure-linux-extensions/blob/b72b251930fc0d62a65a01cf45b8ee5f0f1532d2/Diagnostic/mdsd/mdsdutil/MdsTime.cc#L17)
```
strptime(decoded.c_str(), "%Y-%m-%dT%TZ", &tm);
```

Where as I understand `%T` is short for `%H:%M:%S` where `%S` is

> %S The second (0–60; 60 may occur for leap seconds; earlier also 61 was allowed).

Which does not include the fractional part.

What gives? I cannot simply remove the fractional part from the stamp since it's signed by the storage account access key, but I cannot change the date signed by the function either since it is added by `listAccountSas()`.

Start with /Diagnostic/mdsd/mdsdutil/MdsTime.cc at the referenced strptime call and compare its accepted format with the fractional timestamp shown in extension.log. Reproduce the generated SAS value using the supplied ARM template and inspect the LinuxDiagnostic parsing path. Done means the signed timestamp produced by listAccountSas() is accepted without invalidating the SAS credential.

Scritto dal modello di indicizzazione a partire dal testo della issue.