update exception paths in MDRv2 handlers

sdbusplus::bus::call has no mechanism to distinguish different kinds
of dbus errors. It always throws an SdBusError on any error, with the
appropriate error code set. So these paths were unused and also unable
to build with yocto enabled and without a patched dbus interface
available.

In other sdbusplus error paths, capture the actual exception object and
log e.what() as an entry to provide better logging information.

Tested: run affected mdrv2 commands to see that they still work

Change-Id: I5e8faf73018b4babb5bc56517245edc762f3e09a
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
2 files changed