Fixed issue with stc on initial bootstrap.

Change-Id: Ib29e2cbad776696d991016a288c041a50b992971
diff --git a/tools/test/bin/stc b/tools/test/bin/stc
index 8b26ac8..d7ddc7c 100755
--- a/tools/test/bin/stc
+++ b/tools/test/bin/stc
@@ -12,6 +12,7 @@
 # Download the STC binary if needed
 if [ ! -f $JAR ]; then
     printf "Downloading STC binary..."
+    mkdir -p /tmp/stc
     aux=/tmp/stc/stc-$$.log
     mvn dependency:get -Dartifact=org.onosproject:onos-stc:$VER -Dtransitive=false -B >$aux || fgrep '[ERROR]' $aux
     rm -f $aux