To make a long story short, my (CentOS 7) server's /boot is too small (100MiB) to hold 2 kernels plus the automatically generated rescue image. I want to avoid the hassle of repartitioning and reinstalling my server by preventing the rescue image from being generated. This would leave enough space for at least 2 kernels, and I can still use my hoster's netboot rescue solution should it be needed.
(I know the only 'right' way to deal with this is to fix my partition scheme, but considering the downtime involved with that I wanted to try a more pragmatic solution first)