Stopping parent before reporting

The problem resulted in wrong span durations. The issue was such that for the case where span from request has a parent that needs to be reported we didn't stop that parent. That means that it has value of 'end' equal to 0. In that situation the duration of Span was calculated as a difference between current time and the start time. We should never report spans that have not been stopped - otherwise that stopping will take place a lot of time later.

fixes #247

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/TraceFilter.java

@@ -138,6 +138,7 @@ public class TraceFilter extends OncePerRequestFilter {
 					Span parent =  spanFromRequest.getSavedSpan();
 					if (parent.isRemote()) {
 						parent.logEvent(Span.SERVER_SEND);
+						parent.stop();
 						this.spanReporter.report(parent);
 					}
 				} else {

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/web/TraceFilterTests.java

@@ -184,6 +184,20 @@ public class TraceFilterTests {
 		assertNull(TestSpanContextHolder.getCurrentSpan());
 	}
 
+	@Test
+	public void ensuresThatParentSpanIsStoppedWhenReported() throws Exception {
+		this.request = builder().header(Span.SPAN_ID_NAME, 10L)
+				.header(Span.TRACE_ID_NAME, 20L).buildRequest(new MockServletContext());
+		TraceFilter filter = new TraceFilter(this.tracer, this.traceKeys, spanIsStoppedVeryfingReporter(),
+				this.spanExtractor, this.spanInjector);
+
+		filter.doFilter(this.request, this.response, this.filterChain);
+	}
+
+	SpanReporter spanIsStoppedVeryfingReporter() {
+		return (span) -> assertThat(span.getEnd()).as("Span has to be stopped before reporting").isNotZero();
+	}
+
 	@Test
 	public void additionalMultiValuedHeader() throws Exception {
 		this.request = builder().header(Span.SPAN_ID_NAME, 10L)