Return "is blocking" by default if no frames are matched (#32)

By returning `true` by default, we say "if there are no known frames, we should still consider it a blocking call".
The current implementation misses some blocking calls if the thread is marked but the stacktrace does not contain any blacklisted method (the native agent was returning `JNI_FALSE`)

agent/src/main/java/reactor/blockhound/integration/ReactorIntegration.java

@@ -47,6 +47,7 @@ public void applyTo(BlockHound.Builder builder) {
 
         // `ScheduledThreadPoolExecutor$DelayedWorkQueue.offer` parks the Thread with Unsafe#park.
         builder.allowBlockingCallsInside(ScheduledThreadPoolExecutor.class.getName(), "scheduleAtFixedRate");
+        builder.allowBlockingCallsInside(ScheduledThreadPoolExecutor.class.getName() + "$DelayedWorkQueue", "take");
 
         builder.nonBlockingThreadPredicate(current -> current.or(NonBlocking.class::isInstance));
 

example/build.gradle

@@ -22,6 +22,7 @@ test {
 configurations {
     reactor_3_3_x {
         extendsFrom(testCompile, testRuntime)
+        resolutionStrategy.cacheChangingModulesFor 0, 'seconds'
     }
 }
 
@@ -43,5 +44,7 @@ dependencies {
     testCompile 'junit:junit:4.12'
     testCompile 'org.assertj:assertj-core:3.11.1'
 
-    reactor_3_3_x 'io.projectreactor:reactor-core:3.3.0.BUILD-SNAPSHOT'
+    reactor_3_3_x 'io.projectreactor:reactor-core:3.3.0.BUILD-SNAPSHOT', {
+        changing = true
+    }
 }

native-agent/src/main/cpp/agent.cpp

@@ -116,5 +116,5 @@ extern "C" JNIEXPORT jboolean JNICALL Java_reactor_blockhound_BlockHoundRuntime_
         start_depth += page_size;
     } while (frames_count == page_size);
 
-    return JNI_FALSE;
+    return JNI_TRUE;
 }