libbinder_ndk: more descriptive prune error

We collapse errors into UNKNOWN_ERROR in the NDK API in order to avoid
exposing certain internal details. Now, the log when this happens
includes more information (instead of the code only).

Bug: N/A
Test: see:
    09-22 17:09:29.322  5753  5770 W roid.binder.ct: PruneStatusT:
    Unknown status_t (-129 (Key was rejected by service)) pruned into
    STATUS_UNKNOWN_ERROR
Change-Id: I4f47574857c47341b9500981101adcae75e864c7
diff --git a/libs/binder/ndk/status.cpp b/libs/binder/ndk/status.cpp
index a8ae441..8ed91a5 100644
--- a/libs/binder/ndk/status.cpp
+++ b/libs/binder/ndk/status.cpp
@@ -20,6 +20,7 @@
 #include <android-base/logging.h>
 
 using ::android::status_t;
+using ::android::statusToString;
 using ::android::binder::Status;
 
 AStatus* AStatus_newOk() {
@@ -126,7 +127,7 @@
             return STATUS_UNKNOWN_ERROR;
 
         default:
-            LOG(WARNING) << __func__ << ": Unknown status_t (" << status
+            LOG(WARNING) << __func__ << ": Unknown status_t (" << statusToString(status)
                          << ") pruned into STATUS_UNKNOWN_ERROR";
             return STATUS_UNKNOWN_ERROR;
     }