Fix default log level in echo and load tests

Since we switched to using the `logging` module to log
in pull request #100, none of the messages on the 'INFO'
level were being shown from `tests/echo.py` and
`tests/load.py`, since the default log level is 'WARNING'.

Now, the log level is set to INFO in `tests/echo.py` and
`tests/load.py`, to match the log level in the main websockify
executable.

Fixes #109