Refactoring for libhwbinder test cases

The following files
1. system/libhwbinder/vts/performance/Benchmark_throughput.cpp
2. system/libhwbinder/vts/performance/Latency.cpp

share similar behaviors like class Pipes, struct ProcResults and
similar Process relationship. This patch merges #2 into #1
includes

* accumulated result
* latency percentage bucket

Bug: 37331532
Test: oc-dev on sailfish with following commands
"libhwbinder_latency -i 1 -v"
"libhwbinder_latency -i 10000 -pair 4"
"libhwbinder_latency -i 10000 -pair 4 -trace"

Change-Id: I5d0aa25c0aba4eeb38686305f147c46eab551ec3
1 file changed