Implement 'InstanceId' for LaunchConfiguration

Implement 'InstanceId' for AWS::AutoScaling::LaunchConfiguration
resource to be comcompatible with AWSCloudFormation.

Specification blueprint implement-instanceid-for-launchconfiguration

Change-Id: Icb4cd81e2ece9ec0eb5c3cf24cd4965604d99f0c

specs/kilo/implement-instanceid-for-launchconfiguration.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+==============================================
+Implement 'InstanceId' for LaunchConfiguration
+==============================================
+
+https://blueprints.launchpad.net/heat/+spec/implement-instanceid-for-launchconfiguration
+
+We should support the 'InstanceId' for AWS::AutoScaling::LaunchConfiguration resource
+to be compatible with AWSCloudFormation.
+
+Problem description
+===================
+
+In AWSCloudFormation, user can specify 'InstanceId' property if he wants the
+launch configuration to use settings from an existing instance, see:
+
+http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-as-launchconfig.html
+http://docs.aws.amazon.com/AutoScaling/latest/DeveloperGuide/create-lc-with-instanceID.html
+
+Will be good to implement 'InstanceId' property to be compatible with AWSCloudFormation.
+
+
+Proposed change
+===============
+1. Add 'InstanceId' property, optional and non-updatable
+2. Change 'ImageId' and 'InstanceType' properties to optional
+3. Add the validation of 'InstanceId', 'ImageId' and 'InstanceType', if don't
+   specify 'InstanceId', the other two properties are required
+4. According to the aws developer guide and implementation, allows three cases:
+
+ * Without 'InstanceId', should specify 'ImageId' and 'InstanceType' properties,
+   using the old way to create the new launch configuration.
+
+ * Specify 'InstanceId' only, the new launch configuration has
+   'ImageId', 'InstanceType', 'KeyName', and 'SecurityGroups'
+   attributes from the instance.
+
+ * Specify 'InstanceId' and other properties else, these properties will
+   override the attributes from the instance.
+
+
+Alternatives
+------------
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+huangtianhua <huangtianhua@huawei.com>
+
+Milestones
+----------
+Target Milestone for completion:
+  Kilo-1
+
+Work Items
+----------
+
+* Support the 'InstanceId' property
+* Add UT/Tempest for the change
+
+Dependencies
+============
+
+None