Fix copy/paste error in benchmark code.

This had minimal impact on the results, since 95% of the writes were
performed through pwrite(), but it's important to fix this for future
benchmark suites.

Bug: 29759783
Change-Id: Ic628aab98b9f9def78508cc722899afdefed84ae
diff --git a/bench/benchgen.py b/bench/benchgen.py
index d529332..9a2bcd7 100644
--- a/bench/benchgen.py
+++ b/bench/benchgen.py
@@ -216,7 +216,7 @@
                 # TODO: track actual file size instead of guessing
                 count = min(int(e.args[2]), bufsize)
                 f.size += count
-                print >>bench, 'TEMP_FAILURE_RETRY(read(%s, buf, %d));' % (handle, count)
+                print >>bench, 'TEMP_FAILURE_RETRY(write(%s, buf, %d));' % (handle, count)
                 nwrite += 1
 
         elif e.call == "pread64":