Remove Jack server task dir before creating it

Bug: 22384453
Change-Id: Ief21b18f1ea1769fa5929299a8b953af8245ff6b
diff --git a/tools/jack b/tools/jack
index d201efe..195059e 100755
--- a/tools/jack
+++ b/tools/jack
@@ -86,6 +86,7 @@
 set -o errexit
 
 # Create fifos and files for a task
+rm -rf "$JACK_DIR"
 mkdir  "$JACK_DIR"
 mkfifo "$JACK_OUT"
 mkfifo "$JACK_ERR"