core: use G_SOURCE_REMOVE and G_SOURCE_CONTINUE in GSourceFuncs

plugins/altair/mm-broadband-modem-altair-lte.c

plugins/cinterion/mm-broadband-modem-cinterion.c

plugins/huawei/mm-broadband-bearer-huawei.c

plugins/huawei/mm-broadband-modem-huawei.c

plugins/huawei/mm-plugin-huawei.c

plugins/icera/mm-broadband-bearer-icera.c

plugins/mbm/mm-broadband-bearer-mbm.c

plugins/mbm/mm-broadband-modem-mbm.c

plugins/mbm/mm-sim-mbm.c

plugins/mtk/mm-broadband-modem-mtk.c

plugins/novatel/mm-broadband-bearer-novatel-lte.c

plugins/novatel/mm-broadband-modem-novatel-lte.c

plugins/novatel/mm-common-novatel.c

plugins/option/mm-broadband-bearer-hso.c

plugins/option/mm-broadband-modem-option.c

plugins/pantech/mm-broadband-modem-pantech.c

plugins/sierra/mm-broadband-modem-sierra.c

plugins/sierra/mm-common-sierra.c

plugins/wavecom/mm-broadband-modem-wavecom.c

plugins/zte/mm-broadband-modem-zte.c