When using mbedtls, curl's nonblocking interface will report a request
as done immediately after the socket is written to and never read from
the connection. This will result in a HTTP status code of 0 and zero
length replies. Cherry-pick the patch from curl 7.53.0 to fix this
(https://github.com/curl/curl/commit/b993d2cc).
Fixes https://bugs.openwrt.org/index.php?do=details&task_id=1285.
Signed-off-by: Darren Tucker <dtucker@dtucker.net>
