Propagate keep alive settings from the config

[9seconds]

This PR compliments #441 propagating TCP keep alive to configuration settings.

# this defines a configuration for TCP keep alives. Default values are taken
# from Golang default behavior.
[network.keep-alive]
disabled = false
# idle means a time period after which we start sending TCP Keep Alive probes
idle = "15s"
# interval is a period between 2 consecutive probes
interval = "15s"
# if we miss that many probes, a connection will be considered as a dead one.
count = 9

Very straightforward.