health-check: An automated performance reporting tool

This new target will generated a bootable image that will compute some
system tests to estimate it's efficiency and health status.

A series of raw numbers will be generated and reported inside an
extended hw.py file.

This patch add the required makefile targets, the testing suite (make
health-check).

health-check is today only reporting the cpu performance by using
sysbench.

A typical output is like the following:
('cpu', 'physical_0', 'physid', '1'),
('cpu', 'physical_0', 'cores', '2'),
('cpu', 'physical_0', 'enabled_cores', '2'),
('cpu', 'physical_0', 'threads', '4'),
('cpu', 'physical', 'number', 1),
('cpu', 'logical', 'number', '4'),
('cpu', 'logical_0', 'bogomips', '5187.90'),
('cpu', 'logical_0', 'cache_size', '3072KB'),
('cpu', 'logical_0', 'loops_per_sec', 561),
('cpu', 'logical_1', 'bogomips', '5187.90'),
('cpu', 'logical_1', 'cache_size', '3072KB'),
('cpu', 'logical_1', 'loops_per_sec', 561),
('cpu', 'logical_2', 'bogomips', '5187.90'),
('cpu', 'logical_2', 'cache_size', '3072KB'),
('cpu', 'logical_2', 'loops_per_sec', 553),
('cpu', 'logical_3', 'bogomips', '5187.90'),
('cpu', 'logical_3', 'cache_size', '3072KB'),
('cpu', 'logical_3', 'loops_per_sec', 542),
('cpu', 'logical', 'loops_per_sec', 1604)]

Reporting is spliting physical cpu (sockets) and logical one (thoses
seen by Linux).

Detailed information about physical are only available if seen by lshw.
Bogomips & cache_size are taken from the /proc/cpuinfo while the
loops_per_sec are computed by running sysbench for 10 seconds.

Note that loops_per_sec are reported for
- each logical processor by running binding sysbench on the selected processor but also for
- all logical processors at one time by running sysbench with num-threads = the
  number of logical processors.