Handle GET for instance"s" while some could be being destroyed. 

If an instance (vm) is being destroyed a GET for all instances could fail.

This needs to be fix in rbovirt by adding a rescue in vm_interfaces and
vm_volumes to catch where a vm is being destroyed.

    RHEV-M avoid failure when accessing instances when at the same
    time one or more instances is being destroyed.
    
    Fixes: https://issues.apache.org/jira/browse/DTACLOUD-484