Add option --ipv4

[robmry]

- What I did

TODO

- How I did it

- How to verify it

# docker network create b4
0d4a8723ec72d2d4b661e60c095865fcd77819459ae0e318505fa1feadbae3de
# docker network create --ipv6 b46
b24ceec262cf8c01e0586ebcea3bd440b52fa0f9b1d40c93f8cec189b7674865
# docker network create --ipv6 --ipv4=false b6
cdfdd74fc7f3b5c421894b0c5b33d48ae8517e8edfcaca6fd40a448e801a189d

# docker network ls --format "table {{.ID}}\t{{.Name}}\t{{.Driver}}\t{{.Scope}}\t{{.IPv4}}\t{{.IPv6}}"
NETWORK ID     NAME      DRIVER    SCOPE     IPV4      IPV6
0d4a8723ec72   b4        bridge    local     true      false
cdfdd74fc7f3   b6        bridge    local     false     true
b24ceec262cf   b46       bridge    local     true      true
be4cf667c3a7   bridge    bridge    local     true      false
8f0b062d1967   host      host      local     false     false
08d4868e22d1   none      null      local     false     false

# docker run --rm -ti --network b6 alpine ip a show dev eth0
17: eth0@if18: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue state UP
    link/ether 86:18:48:8f:f3:3d brd ff:ff:ff:ff:ff:ff
    inet6 fd50:8667:92c::2/64 scope global flags 02
       valid_lft forever preferred_lft forever
    inet6 fe80::8418:48ff:fe8f:f33d/64 scope link tentative
       valid_lft forever preferred_lft forever

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.64%. Comparing base (8c22315) to head (afbbecd).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5599      +/-   ##
==========================================
+ Coverage   59.63%   59.64%   +0.01%     
==========================================
  Files         346      346              
  Lines       29208    29216       +8     
==========================================
+ Hits        17417    17425       +8     
  Misses      10822    10822              
  Partials      969      969