pseudomodem: Updated DBus API according to ModemManager API 0.8.

Made the necessary API changes to be compatible with ModemManager API 0.8.

BUG=chromium:246349
TEST=(1) network_3GModemPresent.pseudomodem should pass.
     (2) Running shill against pseudomodem should cause shill to crash
         due to an exception thrown in the DBus proxy layer, saying
         "Error::InvalidArgs".

Change-Id: Iedc6e210548bfc14fb8260fbbd4e5f1b1f49c14b
Reviewed-on: https://gerrit.chromium.org/gerrit/59165
Commit-Queue: Arman Uguray <armansito@chromium.org>
Reviewed-by: Arman Uguray <armansito@chromium.org>
Tested-by: Arman Uguray <armansito@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
4 files changed