vmdk: Allow space in file name

vmdk: Allow space in file name

The previous scanf() format string stopped parsing the file name on the
first white white space, which seems to be allowed at least by VMware
Workstation.

Change the format string to collect everything between the first and
second quote as the file name, disallowing line breaks.

Signed-off-by: Philipp Hahn <hahn@univention.de>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>