Fixes negative performance numbers

Fixes #320
Merge pull request #321 from hazelcast/fix/320-negative-performance-numbers

Fixes negative performance numbers
#322 - fallback to a default init script if no user script is provided
Merge pull request #323 from jerrinot/fix/322-init-script-missing/master

#322 - fallback to a default init script if no user script is provided
Added a test for simulating operation io, but bypassing offloading to operation service