Drivers: hv: utils: Check VSS daemon is listening before a hot backup

Hyper-V host will send a VSS_OP_HOT_BACKUP request to check if guest is
ready for a live backup/snapshot. The driver should respond to the check
only if the daemon is running and listening to requests. This allows the
host to fallback to standard snapshots in case the VSS daemon is not
running.

Signed-off-by: Alex Ng <alexng@messages.microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>