Cannot set initial values for CustomConstraint parameters

[Sudheer Kalla]

While launching a stack from horizon,If the template have custom constraints like below:

parameters:
  TEST_IMAGE:
    type: string
    label: TEST Node Image
    description: SW Image to be used for TEST
    default: TEST_IMAGE
    constraints:
      - custom_constraint: glance.image

The default value is not set in the drop-down created rather than all the available values are listed with out any default value.

The same behavior is seen when we use environment file to load default value for custom constraints.

However form cli it is working fine with out any issue if we use environment file for loading default value for custom constraints