Debian: T640: explicitly add easy-rsa
Debian: T640: explicitly add easy-rsa

easy-rsa is used by e.g. OpenVPN installation and was dropped when enabling
"--apt-recommends false" in VyOS build system. Dependency has been
explicitly added.

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x