polkit: Enable systemd support

polkit: Enable systemd support

By default the polkit will autodetect if systemd is available
and setup the configuraton accordingly, potentially
contaminating sstate.
In this patch systemd is explicitly enabled/disabled.
When enabled, polkit will use systemd for session tarcking,
otherwise it will use ConsoleKit.

(From OE-Core rev: 67c13656343d55ae9d1c79dcace5c79004c4c186)

Signed-off-by: Radu Moisan <radu.moisan@intel.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>