SamsungRIL: Fixes for CDMA data reconnection failures due to stale pppd

Occasionally the CDMA data connection fails to reconnect after various
radio events, which is fixed neither by toggling mobile data nor airplane
mode, but only by a reboot.  One known cause of this problem is that the
pppd_cdma service is occasionally left running after the radio event, which
causes all subsequent "setup data call" operations to fail.  These two
fixes address the stale pppd_cdma service issue:

- Move the pppd_cdma service shutdown (set ril.cdma.data_state=0) from the
  "deactivate data call" response to its request.  This avoids the issue
  where the response never comes (radio crash?), and thus, the service is
  never stopped.

- Force pppd_cdma service shutdown on a "setup data call" failure.  This
  allows subsequent setup attempts to succeed in the event that the
  "deactivate" request was never made (unexpected radio poweroff).