MB-11288: use underscore for option name

python optget package change any option with '-' to '_'

Change-Id: Ib74e6c4dbaefc2272e833e363c21fd42e6486ca2
Reviewed-on: http://review.couchbase.org/37761
Reviewed-by: Bin Cui <bin.cui@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>