Fix svace errors

Fix svace errors

st_things_request_handler.c
- In error statement, make the func to return false

cloud_connector.c
- 'registerPayload' & 'loginoutPayload' are released in 'OCDoResource'
- So, add 'OCRepPayloadDestroy' to release in error state.

easysetup_manager.c
- Add check statement before close file descriptor

resource_handler.c
- change 'strncmp' which is using just for empty checking to 'strlen'

things_req_handler.c
- initialize variable before using

things_security_manager.c
- Add fclose after usage of fds.

things_string_utils.c
- Add '+1' when check string length for null character.