fix antimalware monitoring regression

adds https:// prefix to storage endpoint for proper parsing by
diagnostics extension
add early xml schema validation and improve monitoring logic

Bug fixes:  XML input is now validated in the cmdlet prior to calling
RDFE.   This change also decouples the Monitoring parameter from the
AntimalwareConfiguration parameter, making it more convenient to turn
monitoring on and off.
xsd schema validation enhancement

add support for StorageAccountName and Monitoring elements  (accepted by
the cmdlet even though they are not passed through to RDFE)
Merge pull request #2923 from ejarvi/dev

fix antimalware monitoring regression