rest_at_integration_tests not ran due to typo

There is a typo in narayana.sh, a function called rest_at_integration_tests exists but the script tries to call rest_at_integration_test.

I have commented on the original commit over here:
https://github.com/jbosstm/narayana/commit/34930058e2a3387a0139cd9a45e94c4ff34ea230