test: bump D-Bus service start timeout if we run without accel

test: bump D-Bus service start timeout if we run without accel

The default (25s) doesn't seem to be enough in some cases (especially
in VMs without acceleration), causing spurious timeouts:

[  174.297658] dbus-daemon[647]: [system] Activating via systemd: service name='org.freedesktop.hostname1' unit='dbus-org.freedesktop.hostname1.service' requested by ':1.0' (uid=0 pid=645 comm="hostnamectl " label="kernel")
[  184.202313] systemd[1]: systemd-update-utmp-runlevel.service: Consumed 1.253s CPU time.
[  197.335422] systemd[1]: Started dbus.service.
[  199.211468] testsuite-71.sh[639]: + assert_in 'Static hostname: H' ''
[  199.347192] dbus-daemon[647]: [system] Failed to activate service 'org.freedesktop.hostname1': timed out (service_start_timeout=25000ms)
[  199.394879] testsuite-71.sh[657]: + set +ex
[  199.438918] testsuite-71.sh[657]: FAIL: 'Static hostname: H' not found in:
[  200.966006] systemd-logind[631]: Watching system buttons on /dev/input/event0 (Power Button)
[  201.008178] systemd-logind[631]: Watching system buttons on /dev/input/event1 (AT Translated Set 2 keyboard)
[  201.034106] systemd-logind[631]: New seat seat0.
[  201.238267] sh[658]: + systemctl poweroff --no-block
[  201.329890] systemd[1]: Starting systemd-hostnamed.service...
[  202.156622] systemd[1]: systemd-update-utmp-runlevel.service: Deactivated successfully.
[  204.818913] hostnamectl[645]: Failed to query system properties: Connection timed out
[  205.195583] systemd[1]: testsuite-71.service: Main process exited, code=exited, status=1/FAILURE
[  205.227237] systemd[1]: testsuite-71.service: Failed with result 'exit-code'.
[  205.712780] systemd[1]: Failed to start testsuite-71.service.