AS-288: Check deleted CLB when adding node
treq.json_content using side_effect instead of return_value

since mock_treq now uses side_effect
check PENDING_DELETE also
Refactored CLB or node deletion part - no tests

Moved it into separate function that raises CLBOrNodeDeleted exception
based on error. This is then used in add/remove to succeed/fail the
operation
CLBOrNodeDeleted has RequestError in it for inspection

- spit up LoadBalancerTests into add and remove tests
- Logging only unexpected non-PENDING_UPDATE errors
removed comment - thanks @cyli

According to @cyli: "I think this is still required. I think the fix
just makes it fail faster and with an obvious error, but it will still
fail."
using iter() and simpler message formatting - thanks @lvh
Better name and docstring - per @lvh
Merge branch 'master' into as-288-deleted-clb

Conflicts:
	otter/test/worker/test_launch_server_v1.py
Using mixin instead of Base test class - thanks @lvh

This is because trial will consider LoadBalancerTests as test which is
fine in this case since it doesn't have tests but I guess it is better
design to have it as mixin
using iter instead if list.pop() - thanks @lvh
sphinx class ref - thanks @lvh
Merge pull request #655 from rackerlabs/as-288-deleted-clb

AS-288: Check deleted CLB when adding node (review)