Allows xenapi 'lookup' to look for rescue mode VMs

When you lookup a VM by name, you can specify if you want it to check if
it has a rescue mode instance running.

If it finds the rescue mode instance, it'll return that one instead
of the original name.

This is useful for operations that should work on the rescue mode vm if
it's there, or the normal one, if it's not.

Work towards bug: 1170237
Change-Id: I41b31e59631b78a62faadb9970b6b824929e7061
Can now reboot rescued instances in xenapi

This patch makes it possible to reboot an instance that is in rescue mode.

It causes the reboot action to search first for rescue mode VM (the
normal VMs name plus '-rescue') .. if it can't find it, it does a reboot
of the normal VM. If it finds the rescue one first, it'll reboot the
rescue instance.

If there is more than one VM named 'myvm-rescue', it'll raise an
exception just like it did if there were more than one VM named 'myvm'.

Helps with bug: 1170237

Change-Id: I1858d86bf93546618eeaaec92d856f5236f3f090
Merge "Allows xenapi 'lookup' to look for rescue mode VMs"
Merge "Can now reboot rescued instances in xenapi"