Added default mount_point

Added default mount_point value, since occi.storagelink.deviceid is noptional in OCCI
Merged master fixed conflict.
Merge branch 'stable/havana'
Fix listing of compute resources with unavailable images.

An image of a single instance no longer available (for whatever
reason) caused the entire listing of compute resources to fail. The
problem was that the code requested details about the image by its id,
just to retrieve the id from the details. This can be avoided by using
the id directly.