qdutils/qservice: fix compilation warnings

- fix incorrect type casting.
- remove unused variables.

Change-Id: I4d21fe895b048a9dcb7c43297d44b041ba42d735
diff --git a/libqservice/QServiceUtils.h b/libqservice/QServiceUtils.h
index 2817429..a5f4f7f 100644
--- a/libqservice/QServiceUtils.h
+++ b/libqservice/QServiceUtils.h
@@ -49,7 +49,7 @@
 }
 
 inline android::status_t sendSingleParam(uint32_t command, uint32_t value) {
-    android::status_t err = android::FAILED_TRANSACTION;
+    android::status_t err = (status_t) android::FAILED_TRANSACTION;
     android::sp<qService::IQService> binder = getBinder();
     android::Parcel inParcel, outParcel;
     inParcel.writeInt32(value);