test: give the D-Bus reconnect checks their own integration test

Killing the broker is destructive well beyond the units under test: nothing
reconnects to the new one, so logind for instance keeps running with
org.freedesktop.login1 unowned for the rest of the boot. As a subtest of
TEST-23-UNIT-FILE that leaked into everything running after it, and
statedir.sh, the first one to start user@0.service, then spent 25s per logind
property in user-runtime-dir and, where pam_systemd can't use Varlink, blocked
in CreateSession() past user@.service's 90s TimeoutStartSec and failed — with
the failure pointing at a subtest that has nothing to do with the bus.

In its own test the damage dies with the machine.

test/integration-tests/TEST-95-DBUS-RECONNECT/meson.build

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+integration_tests += [
+        integration_test_template + {
+                'name' : fs.name(meson.current_source_dir()),
+        },
+]

test/integration-tests/meson.build

@@ -111,6 +111,7 @@ foreach dirname : [
         'TEST-92-TPM2-SWTPM',
         'TEST-93-CLONESETUP',
         'TEST-94-COCO',
+        'TEST-95-DBUS-RECONNECT',
 ]
         subdir(dirname)
 endforeach

test/units/TEST-95-DBUS-RECONNECT.sh

@@ -159,3 +159,5 @@ systemctl daemon-reexec
 touch "$marker"
 poll "$unit" SubState running
 systemctl stop "$unit"
+
+touch /testok