bindings.py: Use get_dbus_name to check for error
bindings.py: Use get_dbus_name to check for error

Check the dbus name instead of message for error checking.
The dbus message is the description of the error, like
"Unknown interface 'foo'". The dbus name is the actual
error string, like "org.freedesktop.DBus.Error.UnknownInterface",

Resolves openbmc/openbmc#2463

Change-Id: I8721e7b262dbc8f4ebae9a8e30074bdf6a53b025
Signed-off-by: Adriana Kobylak <742cf4d8dead98b4cab50b088fd2a1406293c958@us.ibm.com>

openbmc/phosphor-objmgr,openbmc/phosphor-objmgr