Improve the workqueue test help message.

The workqueue test help message has two issues. First, the message uses 4 space
indentation when 2 space indentation seems more common. Second, the help
message misses some options.

This commit fixes both issues.

src/test/test_workqueue.c

@@ -300,6 +300,8 @@ help(void)
 {
   puts(
      "Options:\n"
+     "  -h            Display this information\n"
+     "  -v            Be verbose\n"
      "  -N <items>    Run this many items of work\n"
      "  -T <threads>  Use this many threads\n"
      "  -I <inflight> Have no more than this many requests queued at once\n"