When evenly distributing congestion across cells, count the number of
occupied lchans surpassing congestion, and not the overall number of
free lchans -- which disregards congestion thresholds.
Fix the bugs shown by
test_congestion_no_oscillation.ho_vty
test_balance_congestion_tchf_tchh.ho_vty
This implements a simple calculation for congestion load by counting
lchans in use above congestion. An improvement of this calculation
using percent follows in I55234c6c99eb02ceee52be0d7388bea14304930f.
Related: SYS#5259
Change-Id: Icb373dc6bfc9819446db5e96f71921781fe2026d
Also add test_congestion_no_oscillation2.ho_vty which is an almost
identical scenario that does not show the bug -- because it has two more
TCH/H available in BTS 1, showing the strange behavior of the algorithm.
Related: SYS#5259
Change-Id: Idf88b4cf3d2f92f5560d73dae9e59af39d0494c0
Neels Hofmeyr