PowerShell cache files are created at a wrong location

After invoking a function on Azure for the first time, a PowerShell command analysis cache file is created at **D:\home\site\wwwroot**\Microsoft\PowerShell. This is a problem because:

1. Depending on the deployment options, this location may not be writable. In this case, PowerShell will not be able to take advantage of the cache, which may impact execution performance (the impact has not been measured yet, though).
2. When the location is writable, new files appearing under D:\home\site\wwwroot may surprise the user or even break the app.

On Windows, PowerShell command analysis cache files normally appear at C:\Users\\AppData\Local\Microsoft\PowerShell. I suspect the problem on Azure is caused by certain APIs returning an empty string or null instead of ...\AppData\Local on the sandbox.

**D:\home\data** would be a better location for these files.