test: avoid another source of random failures with direct_imap failing to connect on first try

also core src/imap.rs retries connecting (2s with backoff) but direct_imap is only used in (CI) tests
and we can just keep trying every second until pytest timeout hits.

python/src/deltachat/direct_imap.py

@@ -7,6 +7,7 @@ import imaplib
 import io
 import pathlib
 import ssl
+import time
 from contextlib import contextmanager
 from typing import List, TYPE_CHECKING
 
@@ -42,10 +43,14 @@ class DirectImap:
         host = user.rsplit("@")[-1]
         pw = self.account.get_config("mail_pw")
 
-        self.conn = MailBox(host, port, ssl_context=ssl.create_default_context())
-        self.conn.login(user, pw)
-
-        self.select_folder("INBOX")
+        while True:
+            try:
+                self.conn = MailBox(host, port, ssl_context=ssl.create_default_context())
+                self.conn.login(user, pw)
+                self.select_folder("INBOX")
+                return
+            except (OSError, ssl.SSLError, imaplib.IMAP4.error):
+                time.sleep(1)
 
     def shutdown(self):
         try: