Move set_override('root_helper', ...) to base functional class

Change-Id: I0c2223ed2808573ee6b6fe5d56fd965a6e45541f
Print version info at start

When debugging problems from logs, it would be useful to know what
version is running across program start and stop.  In one case I have
a suspicion that an upgrade was run inbetween but the logs don't help
identify that.

My first thought was to grab this from argparse just as --version
does, but that's not really currently possible [1].

The original starting message is probably irrelevant, but I realise
log messages tend to suffer from Hotel California syndrome; you can
check-in but you can never leave.

[1] http://bugs.python.org/issue9399

Change-Id: Ia1bfd2f3589b508e19fd8a94d59beaafd6d657d2
Merge "Print version info at start"
Merge "Move set_override('root_helper', ...) to base functional class"
Merge branch 'master' of https://github.com/openstack/quantum