Improve unit test determinism

… apparently the before/after was a race condition … adding @before seems to have made it better for me.

Author: benjchristensen

rxjava-core/src/main/java/rx/plugins/RxJavaPlugins.java

@@ -20,6 +20,7 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.junit.After;
+import org.junit.Before;
 import org.junit.Test;
 
 /**
@@ -153,6 +154,7 @@ private static Object getPluginImplementationViaProperty(Class<?> pluginClass) {
     public static class UnitTest {
 
         @After
+        @Before
         public void reset() {
             // use private access to reset so we can test different initializations via the public static flow
             RxJavaPlugins.getInstance().errorHandler.set(null);