detect: Adding cpu socket count from lshw

Let's use the physid information reported by lshw to count the number of
physical sockets. This information will be useful for benchmark the
memory.

This commit add also a new test from a real multiple socket setup and
fixes the exisiting one.

That said, macbook pro reports 4 sockets.. I don't really get why.
test_detect: Removing debug trace

print l was only useful for debugging, no need to commit it