handover_test: add test_congestion_favor_best_target_rxlev.ho_vty

The aim is to pin the current basic behavior of handover decision 2,
before modifying the algorithm conditions to fix some bugs in upcoming
patches -- so far no test ensures this particular detail.

Change-Id: I68cdda21ef59c464f0af3c2eee356623e58ea1cd
2 files changed