[lib] Fix timer precision.

Whenever a thread adds an timer funcname_thread_add_timer_timeval() gets called
to add the timer. Before adding the timer a quagga_gettimeofday() call
is made to do some time house keeping. However quagga_gettimeofday() only
updates recent_time, not relative_time that is used to calculate
the alarm_time. Replace with quagga_get_relative (NULL)
diff --git a/lib/thread.c b/lib/thread.c
index 260e8c8..948bc21 100644
--- a/lib/thread.c
+++ b/lib/thread.c
@@ -659,7 +659,7 @@
   thread = thread_get (m, type, func, arg, funcname);
 
   /* Do we need jitter here? */
-  quagga_gettimeofday (&recent_time);
+  quagga_get_relative (NULL);
   alarm_time.tv_sec = relative_time.tv_sec + time_relative->tv_sec;
   alarm_time.tv_usec = relative_time.tv_usec + time_relative->tv_usec;
   thread->u.sands = timeval_adjust(alarm_time);