When using a bridge Tor reports TLS cert lifetime errors (e.g. when
the system clock is way off) with severity "info", but when no bridge
is used the severity is "warn". tordate/20-time.sh depends on grepping
these error messages, so we termporarily increase Tor's logging
severity when using bridge mode. If we don't do this tordate will
sleep forever, leaving Tor in a non-working state.