Free all error queues on shutdown.

As feared, 2bca0988 did cause some leak checkers to get upset about the
state_hash pointer getting cleared.

This change makes err_shutdown free all the error queues to try and
avoid this. Hopefully this doesn't upset TSAN in turn.

BUG=448296

Change-Id: I827da63c793dcabc73168ece052cdcd3d3cc64e3
Reviewed-on: https://boringssl-review.googlesource.com/2890
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>