Currently we pass a reference to a global "rollback" list to create()
to keep rollback functions. Other nodes don't need to know about
global rollback state, and by passing by reference we're giving them
the chance to mess it up for everyone else.
Add a "add_rollback()" function in NodeBase for create() calls to
register rollback calls within themselves. As they hit rollback
points they can add a new entry. lambda v arguments is much of a
muchness -- but this is similar to the standard atexit() call so with
go with that pattern. A new "rollback()" call is added that the
driver will invoke on each node as it works its way backwards in case
of failure.
On error, nodes will have rollback() called in reverse order (which
then calls registered rollbacks in reverse order).
A unit test is added to test rollback behaviour
Change-Id: I65214e72c7ef607dd08f750a6d32a0b10fe97ac3
