Close all logging file descriptors

This has lingered for a long time, finally do something about it...

Change-Id: Ib90408187698d5d4c23ffb0e527011446efc3c7e
diff --git a/stack.sh b/stack.sh
index ab1e8fe..32dac0f 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1419,3 +1419,9 @@
 
 # Indicate how long this took to run (bash maintained variable ``SECONDS``)
 echo_summary "stack.sh completed in $SECONDS seconds."
+
+# Restore/close logging file descriptors
+exec 1>&3
+exec 2>&3
+exec 3>&-
+exec 6>&-