default: Set list to empty instead of None

The `eol_opsys` variable should be set explicitly to the empty list
rather than the implicitly `None` otherwise it causes problems down
the line.

inventory/host_vars/retrace-stg.aws.fedoraproject.org

@@ -24,8 +24,9 @@ faf_opsys_list:
   - centos
 
 # Clean-up packages of following EOLed operating systems
-eol_opsys:
-#  - { opsys: "Fedora", release: "30"}
+eol_opsys: []
+# When not empty, the array should have the following form:
+#   - { opsys: "Fedora", release: "36" }
 
 # GDPR SAR variables
 sar_script: '/usr/bin/faf sar'

inventory/host_vars/retrace03.rdu-cc.fedoraproject.org

@@ -35,8 +35,9 @@ faf_opsys_list:
   - centos
 
 # Clean-up packages of following EOLed operating systems
-eol_opsys:
-#  - { opsys: "Fedora", release: "32"}
+eol_opsys: []
+# When not empty, the array should have the following form:
+#   - { opsys: "Fedora", release: "36" }
 
 # GDPR SAR variables
 sar_script: '/usr/bin/faf sar'

roles/abrt/faf/defaults/main.yml

@@ -240,5 +240,6 @@ faf_web_symboltransfer_packages:
 # EOLed Opsys #
 ###############
 
-eol_opsys:
-  - { opsys: "", release: "" }
+eol_opsys: []
+# When not empty, the array should have the following form:
+#   - { opsys: "Fedora", release: "36" }