Handle D-Bus exceptions

Remove the usage of is_method_error()[1].

Also, add try-catch to handle D-Bus exceptions around mapper call.

[1]https://github.com/openbmc/sdbusplus/blob/master/include/sdbusplus/bus.hpp#L282-L286

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: Id2b5234009e62e6c003f24a25c726317646b582b
2 files changed