Makefile: add -DCONF_debug_memory=0 in order to fix a compilation failure

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Update m->M_dat.MH.MH_pkthdr.len for the outgoing mbuf

Whithout this fix osv-memcached didn't work with EC2 netfront interfaces.

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>