Complete TunerTimeFilter implementation

This CL also set all the successfully closed instance to null
to avoid duplicate closing on the same instance.

Test: make
Bug: 159067322
Bug: 176190508
Change-Id: Idf445641b47f4d8ab4230f30cf6ea3abd4226cbc
diff --git a/services/tuner/TunerLnb.cpp b/services/tuner/TunerLnb.cpp
index 0bfa3fd..4a5acf5 100644
--- a/services/tuner/TunerLnb.cpp
+++ b/services/tuner/TunerLnb.cpp
@@ -97,8 +97,13 @@
         return Status::fromServiceSpecificError(static_cast<int32_t>(Result::UNAVAILABLE));
     }
 
-    Result status = mLnb->close();
-    return Status::fromServiceSpecificError(static_cast<int32_t>(status));
+    Result res = mLnb->close();
+    mLnb = NULL;
+
+    if (res != Result::SUCCESS) {
+        return Status::fromServiceSpecificError(static_cast<int32_t>(res));
+    }
+    return Status::ok();
 }
 
 /////////////// ILnbCallback ///////////////////////