vppinfra: fix coverity issue CID 323952

Type: fix
Fixes: 08600ccfa

Change-Id: I53ba0d96507b55ab7cd735073d6c4cf20a3cc948
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
(cherry picked from commit 05cc62dd504bbb0fb230fcf3786ed7f4d5be2364)

src/vppinfra/unix-misc.c

@@ -148,11 +148,11 @@ clib_file_get_resolved_basename (char *fmt, ...)
 
   r = readlink ((char *) link, buffer, sizeof (buffer) - 1);
   vec_free (link);
-  buffer[r] = 0;
 
   if (r < 1)
     return 0;
 
+  buffer[r] = 0;
   p = buffer + r - 1;
   while (p > buffer && p[-1] != '/')
     p--;