Mark additional tasks info column as deferred
Mark additional tasks info column as deferred

Fields:

- deployment_info;
- cluster_settings;
- network_settings.

in sum take 150Mb for cluster with 200 nodes. Every task
request will create heavy db select, so it will take
a lot of memory, cpu load and dramatically decrease
receiver performance.

With this change this fields will be loaded only if
Nailgun directly required them.

Change-Id: I2417b0370914a0bd3a7f92e897826d9d86e76773
Closes-Bug: #1570509

stackforge/fuel-web,stackforge/fuel-web,stackforge/fuel-web