Avoid running clive TUI while in env set by start_clive_cli.sh

We assume that user will not set CLIVE_BEEKEEPEER__SESSION_TOKEN by
himself. But it will be set by start_clive_cli.sh

Clive TUI will not get notifications from beekeeper, while env var
CLIVE_BEEKEEPER__SESSION_TOKEN is set. It because, it does not own the
notification server endpoint that it is needed while creating session
token.