Add public method isFinished() on JaegerSpan

jaeger-core/src/main/java/io/jaegertracing/internal/JaegerSpan.java

@@ -75,6 +75,12 @@ public long getStart() {
     return startTimeMicroseconds;
   }
 
+  public boolean isFinished() {
+    synchronized (this) {
+      return finished;
+    }
+  }
+
   public long getDuration() {
     synchronized (this) {
       return durationMicroseconds;

jaeger-core/src/test/java/io/jaegertracing/internal/JaegerSpanTest.java

@@ -158,6 +158,12 @@ public void testSetNumberTag() {
     assertEquals(expected, jaegerSpan.getTags().get(key));
   }
 
+  @Test
+  public void testFinished() {
+    jaegerSpan.finish();
+    assertTrue(jaegerSpan.isFinished());
+  }
+
   @Test
   public void testSetTag() {
     jaegerSpan.setTag(new StringTag("stringTag"), "stringTagValue")