Get sandbox group ID for subgroup deletion

This MR gets the gitlab-qa-sandbox-group group ID
to facilitate removing the subgroups

qa/qa/tools/delete_subgroups.rb

@@ -2,9 +2,9 @@
 
 require_relative '../../qa'
 
-# This script deletes all subgroups of a group specified by ENV['GROUP_NAME_OR_PATH']
+# This script deletes all subgroups of a group specified by ENV['TOP_LEVEL_GROUP_NAME']
 # Required environment variables: GITLAB_QA_ACCESS_TOKEN and GITLAB_ADDRESS
-# Optional environment variable: GROUP_NAME_OR_PATH (defaults to 'gitlab-qa-sandbox-group')
+# Optional environment variable: TOP_LEVEL_GROUP_NAME (defaults to 'gitlab-qa-sandbox-group')
 # Run `rake delete_subgroups`
 
 module QA
@@ -47,8 +47,9 @@ module QA
       end
 
       def fetch_group_id
-        group_search_response = get Runtime::API::Request.new(@api_client, "/groups", search: ENV['GROUP_NAME_OR_PATH'] || 'gitlab-qa-sandbox-group').url
-        JSON.parse(group_search_response.body).first["id"]
+        group_name = ENV['TOP_LEVEL_GROUP_NAME'] || 'gitlab-qa-sandbox-group'
+        group_search_response = get Runtime::API::Request.new(@api_client, "/groups/#{group_name}" ).url
+        JSON.parse(group_search_response.body)["id"]
       end
 
       def fetch_subgroup_ids(group_id, group_pages)