Improve test stability.
Improve test stability.

Test cancellation may cause empty line appending to the log file, so clean-up process must skip empty line.

undeadlabs/msgpack-cli,modulexcite/msgpack-cli,undeadlabs/msgpack-cli,msgpack/msgpack-cli,scopely/msgpack-cli,scopely/msgpack-cli,modulexcite/msgpack-cli,msgpack/msgpack-cli