alloc: Use least reserved PDCH for algo A

Currently the slot selection of algorithm A is based on the current
slot usage by active TBF. Especially in the Dl after UL case which
reflects the commen use case "MS initiates TCP connection", the
resulting distribution is not optimal with respect to PDCH usage.

This commit changes the implementation to use the slot reservation
information instead.

Sponsored-by: On-Waves ehf
diff --git a/tests/alloc/AllocTest.cpp b/tests/alloc/AllocTest.cpp
index bf93f57..973ee29 100644
--- a/tests/alloc/AllocTest.cpp
+++ b/tests/alloc/AllocTest.cpp
@@ -586,7 +586,7 @@
 		32, "algorithm B class 10 (DL after UL)");
 
 	test_successive_allocation(alloc_algorithm_a, 1, 1, TEST_MODE_UL_AFTER_DL,
-		7, "algorithm A (UL after DL)");
+		32, "algorithm A (UL after DL)");
 	test_successive_allocation(alloc_algorithm_b, 10, 10, TEST_MODE_UL_AFTER_DL,
 		32, "algorithm B class 10 (UL after DL)");