update default sysctls for 5.10 kernel

[bcressey]

@sam-aws gave us a heads-up that some of the sysctl defaults that are currently set in the kernel will need to be added by userspace for 5.10, if we want to keep them.

# Increasing to account for skb structure growth since the 3.4.x kernel series
net.ipv4.tcp_wmem = 4096 20480 4194304

# Bumped the default TTL to 255 (maximum)
net.ipv4.ip_default_ttl = 255