commander: Fix the position failsafe to a) use proper logic to determine if eph / epv are good or not (the previous logic was in some states not initialized) and b) add a hysteresis time - because the check as it was before had zero hysteresis time for a bad eph / epv value
Merge pull request #907 from PX4/failsafe_fix

commander: Fix the position failsafe to a) use proper logic to determine...