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

awx/main/credential_plugins/conjur.py

@@ -1,4 +1,4 @@
-from .plugin import CredentialPlugin
+from .plugin import CredentialPlugin, CertFiles
 
 import base64
 from urllib.parse import urljoin, quote_plus
@@ -6,11 +6,6 @@ from urllib.parse import urljoin, quote_plus
 from django.utils.translation import ugettext_lazy as _
 import requests
 
-# AWX
-from awx.main.utils import (
-    create_temporary_fifo,
-)
-
 
 conjur_inputs = {
     'fields': [{
@@ -65,22 +60,20 @@ def conjur_backend(**kwargs):
         'headers': {'Content-Type': 'text/plain'},
         'data': api_key
     }
-    if cacert:
-        auth_kwargs['verify'] = create_temporary_fifo(cacert.encode())
 
-    # https://www.conjur.org/api.html#authentication-authenticate-post
-    resp = requests.post(
-        urljoin(url, '/'.join(['authn', account, username, 'authenticate'])),
-        **auth_kwargs
-    )
+    with CertFiles(cacert) as cert:
+        # https://www.conjur.org/api.html#authentication-authenticate-post
+        auth_kwargs['verify'] = cert
+        resp = requests.post(
+            urljoin(url, '/'.join(['authn', account, username, 'authenticate'])),
+            **auth_kwargs
+        )
     resp.raise_for_status()
     token = base64.b64encode(resp.content).decode('utf-8')
 
     lookup_kwargs = {
         'headers': {'Authorization': 'Token token="{}"'.format(token)},
     }
-    if cacert:
-        lookup_kwargs['verify'] = create_temporary_fifo(cacert.encode())
 
     # https://www.conjur.org/api.html#secrets-retrieve-a-secret-get
     path = urljoin(url, '/'.join([
@@ -92,7 +85,9 @@ def conjur_backend(**kwargs):
     if version:
         path = '?'.join([path, version])
 
-    resp = requests.get(path, timeout=30, **lookup_kwargs)
+    with CertFiles(cacert) as cert:
+        lookup_kwargs['verify'] = cert
+        resp = requests.get(path, timeout=30, **lookup_kwargs)
     resp.raise_for_status()
     return resp.text