Fix @CheckReturnValue error in HttpStreamTest

RELNOTES: n/a

--
MOS_MIGRATED_REVID=140527066
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/repository/downloader/HttpStreamTest.java b/src/test/java/com/google/devtools/build/lib/bazel/repository/downloader/HttpStreamTest.java
index ac0351e..5b4f7fa 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/repository/downloader/HttpStreamTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/repository/downloader/HttpStreamTest.java
@@ -126,7 +126,7 @@
     try (HttpStream stream = streamFactory.create(connection, AURL, BAD_CHECKSUM, reconnector)) {
       thrown.expect(IOException.class);
       thrown.expectMessage("Checksum");
-      toByteArray(stream);
+      ByteStreams.exhaust(stream);
       fail("Should have thrown error before close()");
     }
   }