check_printer: Samsung and Sharp printers return empty alerts list when there is no alert

[hapm]

Not sure if this isn't standard behaviour, but as there is an exception for HP printers in the code of check_printer it looks like there are some printer manufacturers that don't return anything when there is no alert. We have Samsung and Sharp printers here, and the alert list is empty for both. I suggest an additional parameter for the alerts command, that allows the list to be empty, so you can allow this behaviour in your check command or service definition.

[riskersen]

Hi, it seems that major printer manufacturer have that behaivor, so i changed the code for that in commit aacbf38