automated: use create_out_dir where appropriate

Change-Id: I10181a7d1ebc53491085d80d67f0cd8f9e43071d
Signed-off-by: Daniel Díaz <daniel.diaz@linaro.org>
diff --git a/automated/linux/signaltest/signaltest.sh b/automated/linux/signaltest/signaltest.sh
index b3b8b1a..0e49c2f 100755
--- a/automated/linux/signaltest/signaltest.sh
+++ b/automated/linux/signaltest/signaltest.sh
@@ -27,8 +27,7 @@
 done
 
 ! check_root && error_msg "Please run this script as root."
-[ -d "${OUTPUT}" ] && mv "${OUTPUT}" "${OUTPUT}_$(date +%Y%m%d%H%M%S)"
-mkdir -p "${OUTPUT}"
+create_out_dir "${OUTPUT}"
 
 # Run signaltest.
 detect_abi