plo: 'Waiting for input' interruption problem

[maska989]

In case where we automate flashing our system, there is problem where host env is too fast and expose some problems with access to plo interruption. In my scenario, target was too fast with detecting first occurrence of "Waiting for input" and execute interruption, but target wasn't ready to collect this behavior.

To reproduce this issue, simply try to execute this pr:
armv7m4: add stlink host reset

Further information in :
test runner for armv7m4-stm32l4x6-nucleo cannot be run on host env
and
trunner: wait for possible plo interruption

[anglov]

Note: it may be connected with arm7m4-stm32l4x6-nucleo target only.