remove the usage of create_temporary_fifo from credential plugins

this resolves an issue that causes an endless hang on with Cyberark AIM
lookups when a certificate *and* key are specified

the underlying issue here is that we can't rely on the underyling Python
ssl implementation to *only* read from the fifo that stores the pem data
*only once*; in reality, we need to just use *actual* tempfiles for
stability purposes

see: https://github.com/ansible/awx/issues/6986
see: https://github.com/urllib3/urllib3/issues/1880

CHANGELOG.md

@@ -7,6 +7,7 @@ This is a list of high-level changes for each release of AWX. A full list of com
 - Removed support for HipChat notifications ([EoL announcement](https://www.atlassian.com/partnerships/slack/faq#faq-98b17ca3-247f-423b-9a78-70a91681eff0)); all previously-created HipChat notification templates will be deleted due to this removal.
 - Fixed a bug which broke AWX installations with oc version 4.3 (https://github.com/ansible/awx/pull/6948/files)
 - Fixed a performance issue that caused notable delay of stdout processing for playbooks run against large numbers of hosts (https://github.com/ansible/awx/issues/6991)
+- Fixed a bug that caused CyberArk AIM credential plugin looks to hang forever in some environments (https://github.com/ansible/awx/issues/6986)
 - Fixed a bug that caused ANY/ALL converage settings not to properly save when editing approval nodes in the UI (https://github.com/ansible/awx/issues/6998)
 - Fixed a bug that broke support for the satellite6_group_prefix source variable (https://github.com/ansible/awx/issues/7031)
 - Fixed a bug in awx-manage run_wsbroadcast --status in kubernetes (https://github.com/ansible/awx/pull/7009)