BucketMonitor connection to use tcp keepAlive.

Upstream part of a connection can crash or become unreachable because
of a network failure. We need to periodically check that the connection
is still alive.

This requires changes of the following tcp settings a machine to make
keepalive more agressive:

/proc/sys/net/ipv4/tcp_keepalive_time (default value is half an hour) -> 60
sec
/proc/sys/net/ipv4/tcp_keepalive_intvl (default value 75 sec) -> 10 sec
/proc/sys/net/ipv4/tcp_keepalive_probes (default value is 9) -> 6 attempts