Fix swap job leak in tests

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJobImplTest.java

@@ -1,6 +1,7 @@
 package uk.ac.ic.wlgitbridge.bridge.swap.job;
 
 import org.apache.commons.io.FileUtils;
+import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
@@ -74,6 +75,13 @@ public class SwapJobImplTest {
         );
     }
 
+    @After
+    public void teardown() {
+        if(swapJob != null) {
+            swapJob.stop();
+        }
+    }
+
     @Test
     public void startingTimerAlwaysCausesASwap() {
         swapJob.lowWatermarkBytes = 16384;