Update return value on application success.

[jlgreathouse]

This PR changes the return values of all of the benchmarks. Right now, if one of the chai programs succeeds, it turns 1. Per generally accepted Unix standards, however, a value of '0' is indicative of success.

See, for instance:
POSIX Standard for exit -- "A value of zero (or EXIT_SUCCESS, which is required to be zero) for the argument status conventionally indicates successful termination."
Linux Documentation - "A successful command returns a 0, while an unsuccessful one returns a non-zero value that usually can be interpreted as an error code"

Returning a non-zero value from these benchmarks makes them difficult to run in scripted systems.