Raise the new OperationTimedOut when futures don't finish
Raise the new OperationTimedOut when futures don't finish

When a future hasn't finished in time it will raise a
specific exception that we should reraise as the new wrapped
error so that users of tooz can nicely handle time outs in
a uniform manner.

Change-Id: Id0b0965e5dcd66e0338fd57294236a14aff4b3d1

openstack/tooz,citrix-openstack-build/tooz,citrix-openstack-build/tooz,openstack/tooz