Change preflight cleanup process to always be run before any run.

Change preflight cleanup process to always be run before any run and add lazy unmount before every run.

Change-Id: If7db175f828fccdd4caa342a0370e842503f16dc

BUG=8015
TEST=Ran it with cbuildbot with/without --clobber with/without old state.

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=dcd1de0

[scottz, 2010-10-22 00:07:31]

LGTM, if you don't want to redo the pipe into stdin of your output that is fine.
It just seems a bit funky.

http://codereview.chromium.org/4007005/diff/1/2
File bin/cbuildbot.py (right):

http://codereview.chromium.org/4007005/diff/1/2#newcode234
bin/cbuildbot.py:234: redirect_stdout=True, error_ok=True)
if you are going to do this, you might as well just pipe it above no?

[sosa, 2010-10-22 00:34:34]

Sadly RunCommand doesn't support piping within a command (at least I
couldn't get it to work)

On Thu, Oct 21, 2010 at 5:07 PM,  <scottz@chromium.org> wrote:
> LGTM, if you don't want to redo the pipe into stdin of your output that is
> fine.
> It just seems a bit funky.
>
>
>
> http://codereview.chromium.org/4007005/diff/1/2
> File bin/cbuildbot.py (right):
>
> http://codereview.chromium.org/4007005/diff/1/2#newcode234
> bin/cbuildbot.py:234: redirect_stdout=True, error_ok=True)
> if you are going to do this, you might as well just pipe it above no?
>
> http://codereview.chromium.org/4007005/show
>

[scottz, 2010-10-22 00:39:10]

Grr that is the other RunCommand. We need to start just porting those features
into this lib otherwise we will never use them.

LGTM