Fixed StepProcessorTest for running on Ubuntu.

Change-Id: If35789d5ca14b06ae808bb73b833ec0212e5dac6
diff --git a/utils/stc/src/test/java/org/onlab/stc/StepProcessorTest.java b/utils/stc/src/test/java/org/onlab/stc/StepProcessorTest.java
index f0c8650..2f04a5d 100644
--- a/utils/stc/src/test/java/org/onlab/stc/StepProcessorTest.java
+++ b/utils/stc/src/test/java/org/onlab/stc/StepProcessorTest.java
@@ -40,7 +40,7 @@
     @BeforeClass
     public static void setUpClass() {
         StepProcessor.launcher = "echo";
-        checkState(DIR.mkdirs(), "Unable to create directory");
+        checkState(DIR.exists() || DIR.mkdirs(), "Unable to create directory");
     }
 
     @AfterClass