test: bump the D-Bus related timeouts to 120s

Let's attempt to reduce the amount of flakes further when the AWS region
we run in is under heavy load and the hypervisor stars stealing our CPU
time.

Follow-up to e0cbb73911 and c78d18215b.

test/test-functions

@@ -1940,12 +1940,12 @@ EOF
 <!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
         "https://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
 <busconfig>
-    <limit name="service_start_timeout">60000</limit>
+    <limit name="service_start_timeout">120000</limit>
 </busconfig>
 EOF
         # Bump the client-side timeout in sd-bus as well
         mkdir -p "$initdir/etc/systemd/system.conf.d"
-        echo -e '[Manager]\nDefaultEnvironment=SYSTEMD_BUS_TIMEOUT=60' >"$initdir/etc/systemd/system.conf.d/bus-timeout.conf"
+        echo -e '[Manager]\nDefaultEnvironment=SYSTEMD_BUS_TIMEOUT=120' >"$initdir/etc/systemd/system.conf.d/bus-timeout.conf"
     fi
 }