VERBOSE is True if true, not 'yes'

fixes bug #1052901

Change-Id: I77b08cbc713cc62808c1ea17aa7f766a56783587
diff --git a/stack.sh b/stack.sh
index 545c071..36c4b9b 100755
--- a/stack.sh
+++ b/stack.sh
@@ -640,7 +640,7 @@
     # Set up output redirection without log files
     # Copy stdout to fd 3
     exec 3>&1
-    if [[ "$VERBOSE" != "yes" ]]; then
+    if [[ "$VERBOSE" != "True" ]]; then
         # Throw away stdout and stderr
         exec 1>/dev/null 2>&1
     fi