CA-73960: avoid allocating debug console for HVM

This will save one event channel per HVM guest in Dom0, since we don't currently make use of it anyway.

Signed-off-by: Marcus Granado <marcus.granado@citrix.com>
Merge pull request #1517 from simonjbeaumont/hfx-918

[HFX-918] CA-73960: avoid allocating debug console for HVM