buildman: Avoid retrying a build if it definitely failed

buildman: Avoid retrying a build if it definitely failed

After a build fails buildman will reconfigure and try again, if it did not
reconfigure before the build. However it doesn't actually keep track of
whether it did reconfigure on the previous attempt.

Fix that logic to avoid a pointless rebuild. This speeds things up quite a
bit for failing builds. Previously they would always be built twice.

Change-Id: Ib37f21320baa7c60bed98f4042c0b7ed7c0dc85e
Signed-off-by: Simon Glass <sjg@chromium.org>