xenapi: fix console for rescued instance

Check if the instance is in vm_state RESCUED and if so
change the name-label to reflect that. Name label is used
to get vm ref and currently the original instance is being
referenced even when in rescue mode. If rescue vm is not ready
yet, InstanceNotReady is raised.

Added tests cases for xenapi get_vnc_console for instance
and rescue mode.

Fixes bug #1157389

Change-Id: I5438103d517c40c1c87ddecd5f88b1487bfc0339
Merge "xenapi: fix console for rescued instance"