matchbox-session-sato: Make the battery applet depend on machine features
matchbox-panel enables the battery plugin only if the
acpi/apm machine features are enabled,
so enable the battery applet in the session script
under the same conditions.
This avoids the 'Failed to load applet "battery"' warning at runtime,
in case these machine features are not defined.
Signed-off-by: Eran Matityahu <eran.m@variscite.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
