INTPYTHON-622 Fix handling of assumed credentials

Author: blink1073

.evergreen/config.yml

@@ -52,7 +52,7 @@ functions:
   "assume role":
     - command: ec2.assume_role
       params:
-        role_arn: ${assume_role_arn}
+        role_arn: ${drivers_test_secrets_role}
 
   "execute tests":
     - command: subprocess.exec
@@ -86,6 +86,7 @@ functions:
 pre_error_fails_task: true
 post_error_fails_task: true
 pre:
+  - func: "assume role"
   - func: "fetch source"
   - func: "fetch secrets"
 post:
@@ -198,15 +199,13 @@ tasks:
     tags: [local]
     commands:
       - func: "fetch repo"
-      - func: "assume role"
       - func: "setup local atlas"
       - func: "execute tests"
 
   - name: test-pymongo-voyageai-remote
     tags: [remote]
     commands:
       - func: "fetch repo"
-      - func: "assume role"
       - func: "setup remote atlas"
       - func: "execute tests"