Take InstanceType for launchconfig res creation

Take the init value of InstanceType for launchconfig
resource creation, since heat will apply nova flavor
custom constraint for launchconfig resource,
see: https://review.openstack.org/#/c/134879/

Change-Id: I23c6032f49104880dc6b424d115ff437f698f5c6
Merge "Take InstanceType for launchconfig res creation"