record cpuinfo

[Antoine Martin]

Makes it easier to know what we're dealing with when getting xpra info or server log samples.

Added in r23050 + r23073.

Problem is that this now causes random server segfaults during startup, possibly as a result of #2341.

(gdb) py-bt
Traceback (most recent call first):
  File "/usr/lib64/python3.7/site-packages/gi/overrides/GLib.py", line 602, in idle_add
    return GLib.idle_add(priority, function, *user_data)
  File "/usr/lib64/python3.7/site-packages/xpra/child_reaper.py", line 150, in sigchld
    self.glib.idle_add(self._sigchld, signum, str(frame))
  File "/usr/lib64/python3.7/selectors.py", line 275, in _key_from_fd
    def _key_from_fd(self, fd):
  File "/usr/lib64/python3.7/selectors.py", line 425, in select
    key = self._key_from_fd(fd)
  File "/usr/lib64/python3.7/multiprocessing/connection.py", line 920, in wait
    ready = selector.select(timeout)
  File "/usr/lib64/python3.7/multiprocessing/popen_fork.py", line 45, in wait
    if not wait([self.sentinel], timeout):
  File "/usr/lib64/python3.7/multiprocessing/process.py", line 140, in join
    res = self._popen.wait(timeout)
  File "/usr/lib/python3.7/site-packages/cpuinfo/cpuinfo.py", line 1297, in _get_cpu_info_from_cpuid
    p.join(0)
  File "/usr/lib/python3.7/site-packages/cpuinfo/cpuinfo.py", line 2152, in get_cpu_info
    CopyNewFields(info, _get_cpu_info_from_cpuid())
  File "/usr/lib64/python3.7/site-packages/xpra/server/mixins/networkstate_server.py", line 124, in init_cpuinfo
    self.cpu_info = get_cpu_info()
  File "/usr/lib64/python3.7/site-packages/gi/overrides/Gtk.py", line 1630, in main
    return _Gtk_main(*args, **kwargs)
  File "/usr/lib64/python3.7/site-packages/xpra/server/gtk_server_base.py", line 107, in do_run
    gtk_main()
  File "/usr/lib64/python3.7/site-packages/xpra/server/server_core.py", line 420, in run
    self.do_run()
  File "/usr/lib64/python3.7/site-packages/xpra/scripts/server.py", line 973, in do_run_server
    r = app.run()
  File "/usr/lib64/python3.7/site-packages/xpra/scripts/server.py", line 445, in run_server
    return do_run_server(error_cb, opts, mode, xpra_file, extra_args, desktop_display)
  File "/usr/lib64/python3.7/site-packages/xpra/scripts/main.py", line 440, in run_mode
    return run_server(error_cb, options, mode, script_file, args, current_display)
  File "/usr/lib64/python3.7/site-packages/xpra/scripts/main.py", line 105, in main
    return run_mode(script_file, err, options, args, mode, defaults)
  File "/usr/bin/xpra", line 26, in <module>
    sys.exit(main(sys.argv[0], sys.argv))

[Antoine Martin]

Fixed in r23163.