efl_net_dialer_http: fix interaction with CURL on receiving data.

efl_net_dialer_http: fix interaction with CURL on receiving data.

When CURLOPT_WRITEFUNCTION returns less then the requested amount,
CURL will fail, not call us back with the remaining data.

Then in such cases we must pause CURL and read nothing.

When unpausing we need to kick curl with timeout action so FD handlers
will be re-arranged.

Last but not least, sync our buffer limit with CURL, otherwise it may
always fail if we're smaller than CURL.