The Kernel instance is the only correct place to ask
for the kernel name. This class has the responsibility
to know information about the selected kernel. The
additional arch based assumption on the kernel name
in the disk builder were wrong. This fixes bnc#1011936
Complete the list of kernel names for the lookup. Normally
the kernel package provides a symlink to the actual kernel
image file. However if the link does not exist we extend the
search to a collection of names for possible kernel images.
The new list now also covers kernel names as used for arm
Along with the change this patch also provides an option to
raise an exception if the kernel lookup did not find any
kernel, which is used for the get_kernel() request in the
dracut initrd system setup where it is mandatory to find
a kernel image.
This fixes bnc#1010874
