tests: run-tests: Do not use sudo if already root

Among other things, sudo can disrupt environment variables that a caller
provides.

Signed-off-by: Brian Norris <briannorris@chromium.org>

tests/hwsim/run-all.sh

@@ -122,7 +122,13 @@ if ! ./start.sh $VM $VALGRIND $TRACE channels=$NUM_CH; then
 	exit 1
 fi
 
-sudo ./run-tests.py -D --logdir "$LOGDIR" $TRACE_ARGS -q $DB $RUN_TEST_ARGS || errors=1
+# Only use sudo if not already root.
+if [ "$(id -u)" != 0 ]; then
+	SUDO=sudo
+else
+	SUDO=
+fi
+${SUDO} ./run-tests.py -D --logdir "$LOGDIR" $TRACE_ARGS -q $DB $RUN_TEST_ARGS || errors=1
 
 ./stop.sh