Move instance_error_causes_group_error() to functional tests

Part of blueprint decouple-nested
Change-Id: I33a9772642c6e58b4b9419330d2aa4e3f8e5cab4
Add some autoscaling crud unit tests

These are basic to get some coverage.

Part of blueprint decouple-nested
Change-Id: I764fedd4371a7a641df98a923b7616df6498c944
Remove duplicate test (it's already in our functional tests)

This test duplicates what is here:
https://github.com/openstack/heat/blob/master/heat_integrationtests/functional/test_update.py#L89-L133

But does not require a full nested stack in unit tests.

Part of blueprint decouple-nested

Change-Id: If5a9d6b1c9dd98b31966312af16587cd148b9c6b
Separate StackWatch out into it's own module

In the interest in small modules that have a matching unit test file.

Part of blueprint decouple-nested
Change-Id: Ia40310007113b1111883a20db99cb7f754ae43bf
Merge "Move instance_error_causes_group_error() to functional tests"
Merge "Add some autoscaling crud unit tests"
Merge "Remove duplicate test (it's already in our functional tests)"
Merge "Separate StackWatch out into it's own module"