Wi-sun Probe update

Stack generate 3 possible probe to new neighbor.

Change-Id: Iaf4177a2d025ace9797a0f5dd88219781bf9ae41

Author: Juha Heiskanen

source/6LoWPAN/ws/ws_bootstrap.c

@@ -995,8 +995,8 @@ static bool ws_neighbor_entry_nud_notify(mac_neighbor_table_entry_t *entry_ptr,
         if (time_from_start > compare_random) {
             activate_nud = true;
         }
-    } else if (etx_entry->etx_samples < 1) {
-        uint32_t compare_random = randLIB_get_random_in_range(0, 8);
+    } else if (etx_entry->etx_samples < 3) {
+        uint32_t compare_random = randLIB_get_random_in_range(1 << etx_entry->etx_samples, 8 << etx_entry->etx_samples);
         if (time_from_start > compare_random) {
             tr_debug("Link Probe test %u with jitter", compare_random);
             activate_nud = true;