Remove duplicate definitions of DEMO_DIR, and define it in the tests
module

This test create a real client and server, use client to call rpc.
Because not include re6stnet, babel_dump related functions aren't tested

see !38 (comment 161622)
for detail.

remove useless test, correct typo and eek problem, refactor verbose
command

see !38

Use the files in demo(dh, fixnemu), and auto create ca, cert, key file

nemu use "%.4x%.3x" % (os.getpid(), n) to generate device name, but it
define the min length not the max length, when pid is high, this will
exceed 16 bytes IFNAMSIZ

network_build: use nemu to create net namespace, provide several network

re6st_wrap: wrap the deploy of re6st node, ease the creation of cert
file and run of the node

test_net contain the tests:
  - ping test: net segment(router), multi-net segment(demo),test after a
    reboot. Because net_demo contain a subnet UPnP, test is not stable.

ping is like ping file in demo, a script to run multiping

registry: add test for RegistryServer and registryClient,
testRegistryServer mainly test methods concerned to http rpc request.
Other methods that call request_dump like getBootStrpPeer is not
include.
testRegistryClient test the rpc call with or not with "cn" parameter.

cli.conf: test each situation call the cli conf.

tunnel: add test for BaseTunnelManager, MultGatewayManager

tools is a util cotain method to make cert and ket files

See merge request !37

See https://www.erp5.com/P-VIFIB-Re6stnet.Roadmap and https://www.erp5.com/P-VIFIB-Re6stnet.Communities

See merge request !36

On Debian < 10:
- debhelper extends postint with 'try-restart', which caused re6st to
  remain stopped after upgrading from a re6st package that stopped
  services unconditionally in prerm (see previous commit);
- deb-systemd-invoke does not check whether the service is enabled
  so 'try-restart' can't be replaced blindly with 'restart'
  (as it is the case in recent Debian).

In addition to minimize re6st downtime, this fixes upgrade from
versions that still use init scripts.

When we drop support for Debian 8, we'll increase debian/compat
and we'll revert this commit.

To prepare for the removal of geoip2, we want nodes to ask the registry
for their country. geoip2 is kept in this update since nodes will still
need to figure out countries of other nodes which haven't updated yet.
Once all nodes will be updated to this version, geoip2 will be ready to
be deleted.

See merge request nexedi/re6stnet!32

If a node restarts and has its address with its country in the cache, it
won't set the _country attribute, and will therefore ignore countries
when making tunnels.

See merge request nexedi/re6stnet!31

Addresses passed to _updateCountry can contain countries if
cache.my_address is used to initialize address in BaseTunnelManager init
function, which causes resolve to be called with too many arguments.