Refactor: move isMemcachedAlive into start_server
Refactor: move isMemcachedAlive into start_server

And use the ASSERT macros to (hopefully) get more information
on _why_ we're failing to start.

Change-Id: Ibf1238cef839a58d4d8408fe2e89b6d2b094927c
Reviewed-on: http://review.couchbase.org/55037
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>

owendCB/memcached,daverigby/kv_engine,couchbase/memcached,daverigby/memcached,couchbase/memcached,owendCB/memcached,daverigby/memcached,couchbase/memcached,daverigby/memcached,daverigby/kv_engine,daverigby/kv_engine,owendCB/memcached,daverigby/kv_engine,owendCB/memcached,daverigby/memcached,couchbase/memcached