zdtm: check that a command completes successfully after a fault (v5)

I suggest to inject a fault and than try to execute the same command
again without a fault to check that it will complete successfully.

v2: skip a parasite blob when we are checking vma-s
v3: remove a loop for two iterations
v4: clean up
v5: call fault hooks from one place
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>