oeqa/concurrencytest: Optimise for autobuilder/clobberdir
We're seeing huge delays on the autobuilder during oe-selftest builddir
deletion. For example there is a currently running selftest we could do
with the results from and its been going 13 hours, at least 8 of which
was in deletion of the builddirs.
There are a variety of ways we could solve this problem however the
autobuilder has a mechanism for deferred deletion, "clobberdir" which
it already uses for this kind of work.
Whilst in general hardcoding things like this is horrible, I believe
in this case the benefits (and resulting improvements on my sanity
if nothing else) mean this is a case where we should do it.
If/as/when someone can come up with a better solution that is fine
and this can be replaced.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
