Request.py: improve instance-state handling.

Does not fail when requested instance is not ready.
Factor code with instance-guid.
KVM SR: resiliency tests: propagate SLA.
KVM SR: resilient profile: allow to propagate SLA.
Resilient stack: remove useless warning.

fixed long ago.
Resilient stack: define different ssh/httpd ports from pbs, import and export. Allow to have import/export using same IP.
resiliency: update TODO.
Resilient recipe: remove hashing of urls/names.

hashing with SHA512 is only intellectual masturbation.
Resilient pbs recipe: rewrite.

Completely rewrite the wrappers generation so that one is able to understand it...
... without spending hours.
Resilient pbs recipe: recover from rdiff-backup failures.
Resilience: add pidfiles in PBS.
KVM SR: add fallback in case of download exception.
KVM SR: Resiliency: Don't stop import if destination file does not exist.

Reverts part of be3b061
Resilient: don't hide exception, print it.
Resilient stack: fill TODO.