MB-16181: Make collections_prototype be dynamic
MB-16181: Make collections_prototype be dynamic

ns_server prototype needs to toggle this to true in response to
a REST API command without reloading memcached.

Change-Id: Ib08b1328b401df183a0776d5360d635863ab51b3
Reviewed-on: http://review.couchbase.org/86191
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine