When TLSv1.3 and session tickets are enabled mbedtls_ssl_read()
will return an error code to inform about a received session ticket.
This can simply be handled like EAGAIN instead of errornously
aborting the connection.

ref: https://github.com/Mbed-TLS/mbedtls/issues/8749Signed-off-by: Anton Khirnov <anton@khirnov.net>