Unbreak and enhance the chroot hypervisor
Unbreak and enhance the chroot hypervisor

When using the chroot hypervisor it turns out, that it is currently
broken/can not be started:

	"Error while executing backend function: Instance test.vm is not
	 running"

The trace from noded.log yields to GetInstanceInfo, which returns a
HypervisorError, when then instance is not running. Fixing this by
returning None like other HVs do.

The second change enhances the console command to use `/bin/sh` as a
chroot shell, which is more likely to be available than `/bin/bash`,
what ever the chroot may contain.

Signed-off-by: Sascha Lucas <159eafbe094024c3a34197db2452d0e30bd5531d@web.de>

ganeti/ganeti,ganeti/ganeti,ganeti/ganeti