[sheepdog] [PATCH] dog: fix confusing code for checking arguments

[Ruoyu]

This command will cause a command line core dump:

dog vdi object location -i 0

As you can see, vdi name is needed as an argument but the above
command don't specify.

The patch fix the bug and others caused by the same reason.

Signed-off-by: Ruoyu <liangry at ucweb.com>
---
 dog/common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/dog/common.c b/dog/common.c
index 13eabd2..dbe2194 100644
--- a/dog/common.c
+++ b/dog/common.c
@@ -256,9 +256,9 @@ int do_generic_subcommand(struct subcommand *sub, int argc, char **argv)
 			}
 		}
 
-		if (flags & CMD_NEED_ARG && argc < 5 + subcmd_depth)
-			subcommand_usage(argv[1], argv[2], EXIT_USAGE);
 		optind++;
+		if (flags & CMD_NEED_ARG && argc == optind)
+			subcommand_usage(argv[1], argv[2], EXIT_USAGE);
 		ret = sub[i].fn(argc, argv);
 		if (ret == EXIT_USAGE)
 			subcommand_usage(argv[1], argv[2], EXIT_USAGE);
-- 
1.8.3.2