[BUG] tls connect/read/write function wrappers unexpectedly set the file descriptor to non-blocking mode.

[xbasel]

tls.c syscall read/write/connect wrappers set the file descriptor to non-blocking mode. These functions should only perform the operation without altering the file descriptor's configuration.

An example where this bug impacted Valkey:
https://github.com/valkey-io/valkey/pull/837/commits

Steps to reproduce the behavior and/or a minimal code sample.

[xbasel]

Code example:

static ssize_t connTLSSyncWrite(connection *conn_, char *ptr, ssize_t size, long long timeout) {
    tls_connection *conn = (tls_connection *)conn_;

    setBlockingTimeout(conn, timeout);
    SSL_clear_mode(conn->ssl, SSL_MODE_ENABLE_PARTIAL_WRITE);
    ERR_clear_error();
    int ret = SSL_write(conn->ssl, ptr, size);
    ret = updateStateAfterSSLIO(conn, ret, 0);
    SSL_set_mode(conn->ssl, SSL_MODE_ENABLE_PARTIAL_WRITE);
    unsetBlockingTimeout(conn); // <--- setting to non-blocking

    return ret;
}