Fix pytest caplog heisenbug introduced in PR #3559 (#3565)

Prior to this PR, this usage of caplog is dependent on the level of
the root logger, which is not set by this test and so ends up being
dependent on which tests have run before: sometimes the INFO logs
output by htex.shutdown are not captured by caplog.

This PR explicitly tells caplog to get at least INFO level logs, to
capture the expected messages.

parsl/tests/test_htex/test_htex.py

@@ -1,3 +1,4 @@
+import logging
 import pathlib
 from subprocess import Popen, TimeoutExpired
 from typing import Optional, Sequence
@@ -107,7 +108,8 @@ def kill_interchange(*args, **kwargs):
 
         mock_ix_proc.terminate.side_effect = kill_interchange
 
-    htex.shutdown()
+    with caplog.at_level(logging.INFO):
+        htex.shutdown()
 
     if started:
         assert mock_ix_proc.terminate.called