sdbusplus::asio: Use the default bus
sdbusplus::asio: Use the default bus

The documentation says that the default bus calls are the ones to use
instead of the open bus calls to reduce resources.

Change-Id: I719494adf2e97e94bb5a9925064cda6cfdd28047
Signed-off-by: Vernon Mauery <4fbc0e9805d36da7c621cd4d73f3eb0d5b12b5f3@linux.intel.com>

openbmc/sdbusplus,openbmc/sdbusplus,openbmc/sdbusplus,openbmc/sdbusplus