tests: ppc: fully fake arch for recovery tests

In commit 8d03325348 we added a new recovery
test, which will work on PPC64 as well as on
X86_64, with basic unit tests.

The tests were supposed to fake the underlying
architecture, but they didn't fully.
This patch completes the job.

Change-Id: Ia8d6e8ccd9a6fb4dec16c547ab2eaa7d33287ba0
Signed-off-by: Francesco Romani <fromani@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/33028
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Petr Horáček <phoracek@redhat.com>