Unify traps in bootstrap scripts to avoid confusion

hack/bootstrap_tfw_dev.sh

@@ -18,8 +18,7 @@ LOGFILE=/tmp/bootstrap_tfw.log
 
 run()
 {
-    trap 'err_cleanup; showlog' ERR
-    trap cleanlog EXIT
+    trap handle_exit EXIT
     : > $LOGFILE
 
     check_dependencies
@@ -37,6 +36,15 @@ run()
     echo "You can build & start TFW by executing the command: ${TEST}/hack/tfw.sh start"
 }
 
+handle_exit()
+{
+    if [[ $? -ne 0 ]]; then
+        err_cleanup
+        showlog
+    fi
+    cleanlog
+}
+
 showlog() { echo && echo "Error! Showing logs:" && cat $LOGFILE; }
 cleanlog() { rm $LOGFILE; }
 err_cleanup() { cd "$BASEDIR" && rm -rf "$BASEIMAGE" "$FRONTEND" "$TEST"; }