AbstractSTestS3AHugeFiles put request assert is using wrong iostatistic

The huge file test case AbstractSTestS3AHugeFiles.test_010_CreateHugeFile() asserts that the put file count > 0. But this stat measures the count of HTTP PUT requests sent to S3; if a multipart PUT was used then the count is zero. As a result, this test case can fail on bigger files than the default.

Fix. assert on OBJECT_PUT_REQUESTS_COMPLETED; this will be 1 for a simple PUT, and #of multipart blocks uploaded on a larger file.