Updated openstack/openstack
Project: openstack/heat  0661277f11b30394828832e1c9cc8f1650322f46

Docs - update JEOS building instructions

As dib-utils has been split from diskimage-builder, the instructions are
no longer complete.

Instead advise users to install diskimage-builder from Github with pip,
solving the dependency problem.

Change-Id: I1319fa08b1f9f026d795fe24325d3d36836b1575