Fix GnuTLS send/recv when returning GNUTLS_E_AGAIN Some values returned from gnutls_record_send() / gnutls_record_recv() indicate that the operation could not be done. In such cases, the error should not propagate to the caller but be operation should be retried. . Upstream fixed this issue in 9e382db87bd1703423760bbe104a66e7cdfcf5a6 with a lot more changes, so this patch only fix the wrong behavior.
Fix GnuTLS send/recv when returning a lower value than expected gnutls_record_send() / gnutls_record_recv() may be interrupted after some data transmission but before the message was completely read/written. When this happen, the value returned by the function is positive but lower that the size of the read/write. In this case, we should not return an error, but rather loop to recv/send the missing data.
