Comment # 17 on bug 1117086 from bob wheater

I checked today and it seem that there are only 3 kernels being kept around
now.
zypp.conf specifies running, latest, latest-1.  Apparently running and latest
must be different and cannot be the same version -- not explicitly specified on
zypp.conf.

purging to 3 kernels is good enough.  Apparently, some update fixed this
problem.  So you can close the case.