bitbake/cooker: Fix parsing failure zombie problem

bitbake/cooker: Fix parsing failure zombie problem

When parsing if a SystemExit event is triggered, it causes the parsing thread to
exit and the main process hangs waiting for it to finish indefintely. Add code to
catch BaseExceptions and raise these with the main process gracefully instead
of just hanging indefinitely with zombie processes.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>