Bug#1108969: sysvinit-utils: add common support for oneshot services in init-d-script helper

[Andrew Bower]

To summarise my previous message:

Looks good; my other thoughts are orthogonal.

The key issue I have is the IDS_RUNDIR which seems over the top to me, 
both the use of the IDS subdirectory (init-d-script being an 
implementation detail for an initscript) and the variable itself, 
instead of just the well-known path /run which could barely be simpler!

Most .pid files seem to be directly under /run, the second most common 
option being under /run/$NAME.

If a daemon has their own subdirectory perhaps they would like to 
override the oneshot file the same way they override PIDFILE, in which 
case we could perhaps justify a ONESHOTFILE variable instead?

In some ways this doesn't matter but would be nice to get it right to 
avoid future --no-stop-on-upgrade scripts from needing maintscript logic 
for switching over.

Andrew