bigquery: format benchmark time in seconds

so all languages look the same

Change-Id: I8fd0797c03a48376c13ca0dd2eb199f0fd09e213
Reviewed-on: https://code-review.googlesource.com/17950
Reviewed-by: Jonathan Amsterdam <jba@google.com>
diff --git a/bigquery/benchmarks/bench.go b/bigquery/benchmarks/bench.go
index ae46a3a..12a12a6 100644
--- a/bigquery/benchmarks/bench.go
+++ b/bigquery/benchmarks/bench.go
@@ -81,5 +81,6 @@
 		}
 		numRows++
 	}
-	log.Printf("query %q: %d rows, %d cols, first byte %s, total %s", qt, numRows, numCols, firstByte, time.Since(startTime))
+	log.Printf("query %q: %d rows, %d cols, first byte %f sec, total %f sec",
+		qt, numRows, numCols, firstByte.Seconds(), time.Since(startTime).Seconds())
 }