Add error strings to catch missed prompts
If a prompt is missed, for example
Hit any key to interrupt autoboot or the bootloader prompt, strings which would be used by subsequent actions can be identified by the waiting action as an error - the DUT has moved ahead of where LAVA expects it. This will save lengthy waits for the next action to timeout.
Migrated from https://projects.linaro.org/browse/LAVA-1395