[5.1.0 CLONE MB-26664]- close tcp connection first and do not close dcp streams when dcp nozzle stops

As of now, when dcp nozzle stops, it closes dcp streams, then closes gomemcached feed, then closed tcp connection for dcp. If the first two operations hang, the tcp connection may not get closed.

The new plan is to close tcp connection first, then close gomemcached feed. There is no need to close dcp streams since tcp connection will cause the dcp streams to be closed by dcp shortly.