ovn build man pages via dist-docs

dist-docs.sh

# docker run -i --tty --rm --net=host --name=ubuntu ubuntu:18.04

DEPS='git automake libtool gcc bc libjemalloc1 libjemalloc-dev 
      libssl-dev llvm-dev libelf-dev libnuma-dev libpcap-dev 
      selinux-policy-dev 
      libunbound-dev libunwind-dev 
      python3 python3-pip man
      ghostscript markdown'

apt update
apt install -y $DEPS
pip3 install --upgrade pip
export PATH="${PATH}:${HOME}/bin:${HOME}/.local/bin"

git clone https://github.com/ovn-org/ovn.git

pushd ./ovn
git submodule update --init
./.ci/linux-prepare.sh
./.ci/linux-build.sh
make dist-docs
popd

ls -l ./ovn/dist-docs