BUG/MINOR: init: properly detect NUMA bindings on large systems

BUG/MINOR: init: properly detect NUMA bindings on large systems

The NUMA detection code tries not to interfer with any taskset the user
could have specified in init scripts. For this it compares the number of
CPUs available with the number the process is bound to. However, the CPU
count is retrieved after being applied an upper bound of MAX_THREADS, so
if the machine has more than 64 CPUs, the comparison always fails and
makes haproxy think the user has already enforced a binding, and it does
not pin it anymore to a single NUMA node.

This can be verified by issuing:

  $ socat /path/to/sock - <<< "show info" | grep thread

On a dual 48-CPU machine it reports 64, implying that threads are allowed
to run on the second socket:

  Nbthread: 64

With this fix, the function properly reports 96, and the output shows 48,
indicating that a single NUMA node was used:

  Nbthread: 48

Of course nothing is changed when "no numa-cpu-mapping" is specified:

  Nbthread: 64

This can be backported to 2.4.