[2.7] certificate_complete_chain: fix stacktrace on parsing error (#49988)

* Fix stacktrace when fail_on_error is False and a file cannot be parsed. (#49987)


(cherry picked from commit 65d5f1a4ef)

* Add changelog.

changelogs/fragments/49987-certificate_complete_chain-error.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- "certificate_complete_chain - fix behavior when invalid file is parsed while reading intermediate or root certificates."

lib/ansible/modules/crypto/certificate_complete_chain.py

@@ -230,6 +230,7 @@ def load_PEM_list(module, path, fail_on_error=True):
             module.fail_json(msg=msg)
         else:
             module.warn(msg)
+            return []
 
 
 class CertificateSet(object):