rilmodem: fix problems with setup data call logic

Change gprs-context's SETUP_DATA_CALL logic to use
the g_ril_unsol_parse_data_call_list() which now properly
handles the case where a non-zero status caused an incorrect
parse failure to be logged.  Also changed the code to use
the correct tech value from the gprs atom when building a
REQUEST_SETUP_DATA_CALL.
unit: move all data_call tests to test-grilunsol.c

Fixed unit tests due to merge of grilreply data_call
parsing code into the grilunsol version that handled
data_call_list change events.  Also re-worked data/voice
registration tests to check RADIO_TECH values as opposed
to the high-level ofono constants.