add warming time for dcb lamps if it has not been used for a long period.

Romain Philippe Lhoussaine ben brahim reports that with some neon dcb data has no lines : visit 85238-85242
Then the lines start to appear in the following exposure and there is no problem after that.

that were short exposures (lamp was turned on for 2s)
It looks like the lamp needs to be warmed up if it hasn't been used for a long period.

I know when the lamp were turned on the last time, so I could add such mechanism.