Fixed typo in an updated test and boundary conditions for StartTransition()

* Fixed the upper boundary condition such that kRouterTransitionDelayMax
  (1200) is included in the possible range of values.
* Allows 0 as a delay minimum for potentially immediate upgrades,
  which the new role transition timer approach now supports, such
  that the valid role transition range is now 0-1200, inclusive of both
  bounds.
* Fixed typo with router2_rejoin_pkt in verify_1_1_5_3_6.py

Author: jthompson-lutron

src/core/thread/mle_ftd.cpp

@@ -4086,15 +4086,15 @@ void Mle::RouterRoleTransition::StartTransition(uint16_t   aRouterTransitionMini
                                                 Transition aTransitionType)
 {
     uint16_t minimumDelay = Min<uint16_t>(aRouterTransitionMinimum, kRouterTransitionDelayMax);
-    if (aRouterTransitionJitter == 0 || minimumDelay == kRouterTransitionDelayMax)
+    if (aRouterTransitionJitter == 0)
     {
-        mTimeout = 1 + minimumDelay;
+        mTimeout = minimumDelay;
     }
     else
     {
-        uint16_t jitter       = Min<uint16_t>(aRouterTransitionJitter, kRouterTransitionDelayMax);
-        uint16_t maximumDelay = Min<uint16_t>(minimumDelay + jitter + 1, kRouterTransitionDelayMax);
-        mTimeout              = 1 + Random::NonCrypto::GetUint16InRange(minimumDelay, maximumDelay);
+        uint16_t jitter          = Min<uint16_t>(aRouterTransitionJitter, kRouterTransitionDelayMax);
+        uint16_t delayUpperLimit = Min<uint16_t>(minimumDelay + jitter, kRouterTransitionDelayMax + 1);
+        mTimeout                 = Random::NonCrypto::GetUint16InRange(minimumDelay, delayUpperLimit);
     }
 
     mTransition = aTransitionType;

tests/nexus/verify_1_1_5_3_6.py

@@ -127,7 +127,7 @@ def verify(pv):
         filter_wpan_src64(ROUTER_2).\
         must_next()
     router2_id_reattached = (router2_rejoin_pkt.mle.tlv.source_addr >> 10)
-    router2_child_id_reattached = router2_pkt.mle.tlv.source_addr & 0x1FF
+    router2_child_id_reattached = router2_rejoin_pkt.mle.tlv.source_addr & 0x1FF
     # Router 2 should only advertise as a router
     assert router2_child_id_reattached == 0