discover mongodb via discovery service, not dns

receiver/unittests/test_request_handler_db_writer.cpp

receiver/unittests/test_statistics_sender_fluentd.cpp

receiver/unittests/test_statistics_sender_influx_db.cpp

.../automatic/high_avail/broker_mongo_restart/check_linux.sh

...utomatic/high_avail/receiver_mongo_restart/check_linux.sh

tests/automatic/settings/broker_settings.json

tests/automatic/settings/broker_settings.json.tpl

tests/automatic/settings/discovery_fixed_settings.json

tests/automatic/settings/discovery_settings.json.tpl

tests/automatic/settings/nginx.conf.tpl

tests/automatic/settings/receiver.json.tpl.lin.in

tests/automatic/settings/receiver.json.tpl.win.in

tests/manual/performance_broker/settings.json

tests/manual/performance_broker/test.sh

tests/manual/performance_full_chain_simple/broker.json

tests/manual/performance_full_chain_simple/receiver.json

tests/manual/performance_full_chain_simple/test.sh

tests/manual/performance_producer_receiver/receiver.json

tests/manual/performance_producer_receiver/test.sh

tests/manual/python_tests/producer/receiver.json.tpl