esp_netif_init() returns standard esp_err_t error code (unlike tcpip_adapter init), so shall be checked for the return value
Also to make the initialization code more consistent.
Current implimentation of esp_http_ota does not perform any error-checking in the data writing phase calls `esp_ota_get_next_update_partition()` irrespetive of the received state of the image. A few additional error checking mechanism have now been added inside the esp_https_ota which returns the control in case an invalid header is received and a wrapper to the function `esp_http_client_is_complete_data_received()` of `esp_http_client` has been added.
