Sync failure when target device was output on uart without host consuming

[linux4life798]

I have noticed that if the target device was output on uart without a consumer on the host, prior to entering the bootloader, ccbootutil fails to sync with the bootloader.
The workaround is to cat the USB serial device before opening with ccbootutil. Could do timeout 0.1 cat /dev/ttyUSB0

TODO:

1. Need to confirm this is not just my machine
2. Check byte stream seen by the Sync method to confirm or reject a buffering problem