[MERGE] stable-2.15 to stable 2.16

['Brian Foley' via ganeti-devel]

commit 3b16955afc001fd3bf06f06edd9e3a7ea013ab60
Merge: a1ae7d3 236a237
Author: Brian Foley <bpfo...@google.com>
Date:   Mon Aug 22 12:08:27 2016 +0100

    Merge branch 'stable-2.15' into stable-2.16
    
    * stable-2.13
      Bugfix: migrate needs HypervisorClass, not an instance
    
    Signed-off-by: Brian Foley <bpfo...@google.com>