core: make Auto config load balancer not depend on service config

Also, add some tests
diff --git a/core/build.gradle b/core/build.gradle
index bdc09c5..b94e5df 100644
--- a/core/build.gradle
+++ b/core/build.gradle
@@ -28,7 +28,8 @@
     }
 
     testCompile project(':grpc-context').sourceSets.test.output,
-            project(':grpc-testing')
+            project(':grpc-testing'),
+            project(':grpc-grpclb')
 
     signature "org.codehaus.mojo.signature:java16:1.1@signature"
 }