lib/oe/reciputils.py: parallelize upstream version checks

lib/oe/reciputils.py: parallelize upstream version checks

Previously this was done via bitbake tasks, and when this
was rewritten to a for loop, performance sufered significantly:
from 90 seconds to about 12 minutes for oe-core. This change
restores the previous run time, and makes it possible
to perform such checks with command line utilities in an
interactive way.

Implementation note: we have to create a copy of the recipe
data, as Tinfoil API can't be used from multiple threads
and only allows one process to access the data at a time.

Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>