stdout-flush-wrapper.sh: Bump sleep to 8s

This seems to be reliable figure, based on testing.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I347558f67f4014819422f29d85be5822e6348e74
diff --git a/stdout-flush-wrapper.sh b/stdout-flush-wrapper.sh
index 9729cf8..7a7a44d 100755
--- a/stdout-flush-wrapper.sh
+++ b/stdout-flush-wrapper.sh
@@ -9,4 +9,4 @@
 cmd="$1"
 shift
 stdbuf -oL "$cmd" "$@"
-sleep 5
+sleep 8