zebra: count iface up/down events and keep last time of their occurrence

It is quite useful to be able to assert whether specific interfaces have
flapped or also to verify that specific interfaces have not flapped.

By having counters for those events and storing the last time of their
occurrence, this is made possible.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Tested-by: NetDEF CI System <cisystem@netdef.org>
diff --git a/zebra/main.c b/zebra/main.c
index f3c08f1..8370732 100644
--- a/zebra/main.c
+++ b/zebra/main.c
@@ -440,7 +440,10 @@
   /* Don't start execution if we are in dry-run mode */
   if (dryrun)
     return(0);
-  
+
+  /* Count up events for interfaces */
+  if_startup_count_up ();
+
   /* Clean up rib. */
   rib_weed_tables ();