MB-10217: Use erts-5.8.x on Mac

We are currently using R14B04 which bundles erts-5.8.5. For some
reason, the Mac package was using erts-5.9.x which is not correct.
Changing it back to erts-5.8.x to match the official version.

Change-Id: I6e7390e94d3ccd27c46714bcbdda0f822d4822da
Reviewed-on: http://review.couchbase.org/33921
Reviewed-by: Brett Lawson <brett19@gmail.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Sriram Melkote <siri@couchbase.com>