ATF setting values to list collector variable does not work and generates the error "Not able to submit as mandatory field is not filled"

In ATF setting values to list collector variable is not working with the error "Not able to submit as mandatory field is not filled".

1. Create a new test case.
2. Write an ATF step to open existing catalog item such as "Report Mass Outage".
3. Write an ATF step to fill values to the catalog item using "Set Variable Values" step configuration.
4. Provide the sys_IDs in comma separated format as input parameter in step config.
5. Write a step to submit catalog.
6. Run the test case. The execution will fail with error "Not able to submit as mandatory field is not filled", due to a mandatory field "Which Servers are impacted?" which is a list collector that was not filled in steps 3-4.

As documented in Types of service catalog variables, g_form.setValue() is not supported for List Collector Variable if it is of type slushbucket. List Collector with glide_list attribute works correctly with the g_form.setValue() api. ATF uses the g_form API so, if g_form is not supported for a variable, the ATF for that Variable will not run.

As a workaround, set glide_list as attribute for the List Collector. 

NOTE: This modifies metadata and will affect all users.