libcurl-7.66.0 and older returns CURLE_WRITE_ERROR when a server
responds with unknown or unsupported Content-Encoding (see [1] and [2]).
This was fixed in future libcurl-7.67.0 and proper
CURLE_BAD_CONTENT_ENCODING code will be returned in this case.

We should process the code in the same way as we do for
CURLE_WRITE_ERROR.

[1]: curl/curl#4310
[2]: curl/curl#4449

Closes #4579

Reviewed-by: Alexander Turenko <alexander.turenko@tarantool.org>