Add block transfer status

[simosillankorva]

• add status for successfull and failing block case
• call sn_coap_rx_callback when block transfer is done or fails
• this enables the user of the library to know what happened to the blocks.

[anttiylitokola]

@simosillankorva, sn_coap_protocol unit tests are failing, could you check that one? 10:20:36 rm -f objs/sn_coap_protocol_unit/sn_coap_protocol.gcda objs/sn_coap_protocol_unit/main.gcda objs/sn_coap_protocol_unit/libCoap_protocol_test.gcda objs/sn_coap_protocol_unit/sn_coap_builder_stub.gcda objs/sn_coap_protocol_unit/sn_coap_parser_stub.gcda objs/sn_coap_protocol_unit/sn_coap_header_check_stub.gcda objs/sn_coap_protocol_unit/ns_list_stub.gcda objs/sn_coap_protocol_unit/randLIB_stub.gcda gcov_output.txt gcov_report.txt gcov_error.txt ; echo "Running sn_coap_protocol_unit_tests"; ./sn_coap_protocol_unit_tests -ojunit | tee sn_coap_protocol_unit_tests.txt 10:20:36 Running sn_coap_protocol_unit_tests 10:20:36 Segmentation fault (core dumped)

There is some Jenkins configuration issue since it still reports everything is ok.

[anttiylitokola]

rebuild

[simosillankorva]

Fixed the issue that caused the unit test to crash + added comments and tried to clarify the code.

[yogpan01]

@artokin @terhei Can you check if this change is ok with CoAP service for Thread as well ?

[terhei]

CoAP service does not support blockwise, so this is OK.