Refactor: Simplify subdoc_create_context
Refactor: Simplify subdoc_create_context

Call out into a helper function for each of the two paths
instead of keeping the entire impl in the switch.

Change-Id: I12be670af68e13738b5dc780dc3071d496aa0611
Reviewed-on: http://review.couchbase.org/70254
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>

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