Improve error reporting from "rbd feature enable/disable"
Pull request ID:
For example, attempting to enable the journaling feature on an image that doesn't have the exclusive-lock feature enabled results in the following:
rbd: failed to update image features: (22) Invalid argument 2016-05-11 09:13:40.317719 7f8c53de7d80 -1 librbd: cannot enable journaling
The error message should explain the missing dependency.