Cannot see function key in the portal during cold start

[watashiSHUN]

before we finish indexing all methods, portal will display 404 when trying to retrieve function keys. Reproducible with cold starts (ie, after fresh deployment)

Repro steps

1. To mimic cold start, first, break the host by providing a malformed host.json
   
2. Go to portal, function key is missing
   
   

in order to retrieve function key, we don't need to wait for indexing, instead we can do everything at file system level:

azure-functions-host/src/WebJobs.Script.WebHost/Controllers/KeysController.cs

Lines 91 to 99 in 1376998

	private async Task<IDictionary<string, string>> GetFunctionKeys(string functionName)
	{
	if (!_scriptHostManager.Instance.IsFunction(functionName))
	{
	return null;
	}
	return await _secretManager.GetFunctionSecretsAsync(functionName);
	}

[mathewc]

Likely related to the work we did for #2114. Though that was done long ago.