With the new server structure we no longer need this separate
environment init script. Just set BB_SERVER_TIMEOUT to be greater
than zero and bitbake will remain in memory and the UI will auto-reconnect
to it.

Also clean out the old shutdown code from oe-init-build-env which
also doesn't make sense now.

(From OE-Core rev: a17724d687f9c04dc21f2f369da2b492f7119ba0)

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