meek-client-torbrowser should always use TOR_BROWSER_TOR_DATA_DIR
Currently, we only use the TOR_BROWSER_TOR_DATA_DIR env var on OSX. When we move user data out of the Browser directory on Linux and Windows, we should clean up the meek-client-torbrowser code so that the meek browser profile path is always constructed using the env var. See ticket:19646#comment:15 for more background.