ioemu: Stop PV guest from parsing xenstore and opening block devices.

ioemu: Stop PV guest from parsing xenstore and opening block devices.

PV guests are now using QEMU for a vncserver.  During initialization
of QEMU xenstore_parse_config() is being called causing PV guests to
open block devices.  This patch makes a new function,
xenstore_daemon_open(), so that the vnc password functions have an
open xenstore handle and moves xenstore_parse_config() into the FV
machine specific init function.

Signed-off-by:  Pat Campbell <plc@novell.com>