Ensure we don't access the net when building docs

(Note, this has not been sent upstream)

Change-Id: I9d02fb4053a8106672aded1614a2850e21603eb2
remove runtime dep on python-pbr

Change-Id: I6f247f64c561d49c13e3c2f67401fe150b6d47b6
Use updated parallel install versions of epel package

Use SQLAlchemy >= 0.7.8 WebOb >= 1.2 Routes >= 1.12.3 PasteDeploy >= 1.5.0
and depend on the parallel installable versions of these packages to satisfy
those requirements.
Remove unnecessary steps for cold snapshots

Up until now when we created cold snapshots we were stopping the
instance, create an internal snapshot, extract the snapshot to a file
and then delete the internal snapshot before bringing up the instance.

If the instance is shut down, there's no concurrent writer, so the image
can be directly extracted without taking an internal snapshot first,
because the snapshot and the current state are the same.

In this patch the creation and deletion of the internal snapshot are
removed to eliminate the extra steps and optimize the creation of
snapshots a bit.

Closes-Bug: #1242819
Closes-Bug: #1247185

Change-Id: I429fa2e1e26aea321eecbf14edd11263fff525ae
(cherry picked from commit 8c985874c7885f31871204d3f83ce547fefc5fb6)

Conflicts:
	nova/virt/libvirt/imagebackend.py