{on,off,reboot}delay needs standardization

[biergaizi]

Many NUT drivers accept the options ondelay, offdelay, and rebootdelay at startup. But unlike their runtime equivalent (ups.delay.start, ups.delay.reboot and ups.delay.shutdown), it seems that there is currently no project-wide standard or documentation to specify their acceptable uses. The most common behavior in existing drivers is to parse them at startup and convert them to ups.delay.*. But due to the lack of standard, it's not guaranteed and occasionally confusions among developers and users arise. For example, in bug #957, the riello_usb and riello_ser drivers attempt to read ups.delay.start, but this variable is not initialized anywhere in the driver, nor the driver accept ondelay, causing a NULL pointer dereference - instead, it requires default.ups.delay.start, much to the surprise of the user.

Another potential benefit is reducing code duplication - every driver has its own parser to do same thing over and over, if we can have a standardized delay option, main.c can do it automatically.

The standard should address the following issues.

1. Do we still really need {on,off,reboot}delay when we already have default.ups.delay.start to set these delays?
2. If we decided to keep {on,off,reboot}delay, when must a driver accept them as options? This needs to be a standard. My idea: if ups.delay.start is writable, the driver must have ondelay, etc.
3. Alternatively, perhaps the use of {on,off,reboot}delay should be discouraged and phased out. We can implemented the old options as a wrapper for the standardized default.ups.delay in main.c, only for backwards compatibility.