Further increase systemd service hardening
Further increase systemd service hardening

Disable use of namespaces, control groups, addresses families that aren't used, kernel module loading, and setting of kernel tunables.
bpzhang/memcached,gencer/memcached,elfchief/memcached,elfchief/memcached,elfchief/memcached,dormando/memcached,gencer/memcached,gencer/memcached,memcached/memcached,memcached/memcached,dormando/memcached,guikcd/memcached,memcached/memcached,memcached/memcached,guikcd/memcached,gencer/memcached,memcached/memcached,dormando/memcached,guikcd/memcached,bpzhang/memcached,bpzhang/memcached,elfchief/memcached,dormando/memcached,bpzhang/memcached,guikcd/memcached,guikcd/memcached,dormando/memcached,gencer/memcached,elfchief/memcached