TEST-04-JOURNAL: use bash to make builtin echo command used

When non-builtin echo command is used, then the command may exit before
journald find the source of the stream, and the log filtering may not be
applied.

Hopefully fixes #37143.

test/integration-tests/TEST-04-JOURNAL/TEST-04-JOURNAL.units/logs-filtering.service

@@ -5,6 +5,6 @@ Description=Log filtering unit
 Type=oneshot
 # If the service finishes extremely fast, journald cannot find the source of the
 # stream. Hence, we need to call 'journalctl --sync' before service finishes.
-ExecStart=sh -c 'echo "Logging from the service, and ~more~ foo bar"; journalctl --sync'
+ExecStart=bash -c 'echo "Logging from the service, and ~more~ foo bar"; journalctl --sync'
 SyslogLevel=notice
 LogLevelMax=info

test/units/delegated_cgroup_filtering_payload.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # SPDX-License-Identifier: LGPL-2.1-or-later
 
 mkdir /sys/fs/cgroup/system.slice/delegated-cgroup-filtering.service/the_child