vtysh, zebra: Fix link-params to use exit-link-params

Fix the link-params submode to use the 'exit-link-params'
to indicate we are exiting a submode.

Fixup all the relevant bits.
diff --git a/vtysh/vtysh_config.c b/vtysh/vtysh_config.c
index e6d8823..2834ef4 100644
--- a/vtysh/vtysh_config.c
+++ b/vtysh/vtysh_config.c
@@ -190,7 +190,7 @@
 	      config->index = LINK_PARAMS_NODE;
 	    }
 	  else if (config->index == LINK_PARAMS_NODE &&
-	           strncmp (line, "  exit", strlen ("  exit")) == 0)
+	           strncmp (line, "  exit-link-params", strlen ("  exit")) == 0)
 	    {
 	      config_add_line (config->line, line);
 	      config->index = INTERFACE_NODE;