Disable IPv6 when using apt-get

Sometimes when run command apt-get update, it connected to some repo using IPv6 address. But it made long delay because ISP's network was not ready for IPv6.
Config make use IPv4
- Add -o Acquire::ForceIPv4=true when run apt-get
- Make config persistent:

# echo 'Acquire::ForceIPv4 "true";' | tee /etc/apt/apt.conf.d/99force-ipv4