MB-6301 Flush buffers periodically
MB-6301 Flush buffers periodically

By default it will flush it's buffer every minute, but
you may change the interval with the sleeptime parameter:

sleeptime=nnn

where nnn is the number of seconds to wait between flushing
the buffer.

Change-Id: I8619c2d7578002213cc03bc5fdfb6b66908aa56c
Reviewed-on: http://review.couchbase.org/19864
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

owendCB/memcached,jimwwalker/memcached,couchbase/memcached,daverigby/kv_engine,mrkwse/memcached,daverigby/kv_engine,abhinavdangeti/memcached,couchbase/memcached,daverigby/kv_engine,owendCB/memcached,mrkwse/memcached,abhinavdangeti/memcached,owendCB/memcached,daverigby/memcached,mrkwse/memcached,cloudrain21/memcached-1,abhinavdangeti/memcached,cloudrain21/memcached-1,couchbase/memcached,abhinavdangeti/memcached,cloudrain21/memcached-1,cloudrain21/memcached-1,jimwwalker/memcached,abhinavdangeti/memcached,mrkwse/memcached,owendCB/memcached,daverigby/memcached,daverigby/kv_engine,daverigby/memcached,daverigby/memcached,couchbase/memcached,jimwwalker/memcached