Problem: Can't use configuration in packages
Problem: Can't use configuration in packages

This is different fix following up on c687d0a. c687d0a fixed service
files generated for local installation - aka just normal configure and
make install into /usr/local but it broke installation in packages where
system config directory is explicitly overridden to end up with
configuration in etc.

Solution: Return to the previous solution using sysconfdir but also
exporting prefix variable so it should work in both cases.

paddor/zproject,twhittock/zproject,zeromq/zproject,keent/zproject,paddor/zproject,taotetek/zproject,eburkitt/zproject,keent/zproject,taotetek/zproject,asokoloski/zproject,zeromq/zproject,hintjens/zproject,taotetek/zproject,zeromq/zproject,twhittock/zproject,miska/zproject,eburkitt/zproject,hintjens/zproject,paddor/zproject,asokoloski/zproject