MB-7013: Make test less fragile

There's one test that would fail on Apache CouchDB, as the number
representation of the output is currently different. Hence parse
the output to Erlang to get rid of those differences.

Change-Id: I75b4611101a9c31732de58916bd521a9d4c29c54
Reviewed-on: http://review.couchbase.org/22990
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>