doc, vtysh: Fixup of history handling

This fix does two things:

1) If the ${HOME}/.history_quagga file does not exist, create it
for history storing.
2) Allow vtysh -c "..." commands to be stored in history file
as well

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/vtysh/vtysh_user.c b/vtysh/vtysh_user.c
index 7e10d68..239a633 100644
--- a/vtysh/vtysh_user.c
+++ b/vtysh/vtysh_user.c
@@ -191,6 +191,16 @@
   return 0;
 }
 
+char *
+vtysh_get_home (void)
+{
+  struct passwd *passwd;
+
+  passwd = getpwuid (getuid ());
+
+  return passwd ? passwd->pw_dir : NULL;
+}
+
 void
 vtysh_user_init (void)
 {