Limit tcp_max_tw_buckets to avoid connection issues between services

[nikosmichas]

Related to #211

By changing the value we enforce the OS to kill sockets that remain in TIME_WAIT state and do not allow the services to open new sockets.

       tcp_max_tw_buckets (integer; default: see below; since Linux 2.4)
              The maximum number of sockets in TIME_WAIT state allowed in
              the system.  This limit exists only to prevent simple denial-
              of-service attacks.  The default value of NR_FILE*2 is
              adjusted depending on the memory in the system.  If this
              number is exceeded, the socket is closed and a warning is
              printed.

A good explanation on a similar case can be found here https://www.percona.com/blog/2014/12/08/what-happens-when-your-application-cannot-open-yet-another-connection-to-mysql/