Use S2N_SMALL_FRAGMENT_LENGTH in ChaCha20 tests
Use S2N_SMALL_FRAGMENT_LENGTH in ChaCha20 tests

Brings the test up to speed with changes added by #371

alexeblee/s2n,bpdavidson/s2n,PKRoma/s2n,bpdavidson/s2n,awslabs/s2n,wcs1only/s2n,awslabs/s2n,alexeblee/s2n,raycoll/s2n,wcs1only/s2n,bpdavidson/s2n,PKRoma/s2n,jldodds/s2n,wcs1only/s2n,gibson-compsci/s2n,alexeblee/s2n,raycoll/s2n,colmmacc/s2n,raycoll/s2n,wcs1only/s2n,alexeblee/s2n,wcs1only/s2n,raycoll/s2n,jldodds/s2n,gibson-compsci/s2n,colmmacc/s2n,PKRoma/s2n,colmmacc/s2n,raycoll/s2n,awslabs/s2n,PKRoma/s2n,jldodds/s2n,jldodds/s2n,raycoll/s2n,colmmacc/s2n,gibson-compsci/s2n,bpdavidson/s2n,gibson-compsci/s2n,jldodds/s2n,awslabs/s2n,colmmacc/s2n,gibson-compsci/s2n,PKRoma/s2n,gibson-compsci/s2n,PKRoma/s2n,PKRoma/s2n,alexeblee/s2n,wcs1only/s2n,bpdavidson/s2n,bpdavidson/s2n,awslabs/s2n,colmmacc/s2n,alexeblee/s2n,wcs1only/s2n,wcs1only/s2n,PKRoma/s2n,awslabs/s2n