monitor: Report encrypted disks in snapshot mode (Jan Kiszka)

If the backing file is encrypted, 'info block' currently does not report
the disk as encrypted. Fix this by using the standard API to check disk
encryption mode. Moreover, switch to a canonical output format.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6706 c046a42c-6fe2-441c-8c8c-71466251a162
