Be clearer about customising downloaded images.

We wouldn't want someone customising their local shell...

Change-Id: I8d870140a4c43527e78c131014d2daac9bd79c09
Advise folk to sit in $TRIPLE_ROOT not incubator.

The incubator directory shouldn't be assumed to be the working
directory as our tools need to be installable.

Telling folk to cd to it makes it special and increases the chance of
accidentally making code assume it is the working directory.

Change-Id: Ib09407e1ce97fa5fd12d4b7387e57d04e9f002d3
Fix a small typo.

Change-Id: Ifd05af9026daf54ba5c5707954cc695cb756f8a3
Stop copying stackrc out of clouds.

The static stackrc we embed in cloud images isn't suitable for using
from outside the cloud, instead we make one in the incubator which is.
We already did that for the under and overclouds, now do it for the
seed cloud too.

Fixes bug 1191650

Change-Id: Id5b6fa77191e5231df77192a900059069ebef6c6