[cleanup] convert bzero() deprecated by POSIX to memset()

autoscan 2.62 complains about bzero(), so a good fix
nowadays is to just replace it.
diff --git a/isisd/isis_lsp.c b/isisd/isis_lsp.c
index 48e3147..50289db 100644
--- a/isisd/isis_lsp.c
+++ b/isisd/isis_lsp.c
@@ -769,7 +769,7 @@
   /* for the hostname tlv */
   if (lsp->tlv_data.hostname)
     {
-      bzero (hostname, sizeof (hostname));
+      memset (hostname, 0, sizeof (hostname));
       memcpy (hostname, lsp->tlv_data.hostname->name,
 	      lsp->tlv_data.hostname->namelen);
       vty_out (vty, "  Hostname: %s%s", hostname, VTY_NEWLINE);