vtysh: service integrated-vtysh-config not being written to file

The vtysh commands:
service integrated-vtysh-config
hostname XXXX

were not being written to the /etc/quagga/Quagga.conf file with a wr mem
when service integrated-vtysh-config was issued.  This patch fixes this
issue

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/vtysh/vtysh.c b/vtysh/vtysh.c
index ad1657f..2e2203d 100644
--- a/vtysh/vtysh.c
+++ b/vtysh/vtysh.c
@@ -1957,6 +1957,7 @@
   for (i = 0; i < array_size(vtysh_client); i++)
     vtysh_client_execute (&vtysh_client[i], line, NULL);
 
+  vtysh_config_write ();
   vtysh_config_dump (fp);
 
   fclose (fp);