Allow to pass the flush tests using the tty0tty virtual devices
Allow to pass the flush tests using the tty0tty virtual devices

The receiver on other side should be opened even if it is not used;
otherwise the tests will be fails with the EINVAL error.

(cherry-picked from a5114f9a9249c5f3263c848d96600ea8e30f22da)
Change-Id: I85ff942c5b7e8276f22867921239bfc8933dac77
Reviewed-by: Denis Shienkov <6a9c747bd2ba446682324cf340d3b86f30cf4d55@gmail.com>

RoadWorksSoftware/QtSerialPort-OS2,RoadWorksSoftware/QtSerialPort-OS2