kernel-install: add compat with 'installkernel'

If 'kernel-install' is called as 'installkernel' it will be compatible with the
syntax used by the kernel's build system.

This means it can be called by doing 'make install' in a kernel build
directory, if the correct symlink has been installed (which we don't do by
default yet).

[Edit harald@redhat.com: removed basename and use shift]

src/kernel-install/kernel-install

@@ -54,9 +54,15 @@ dropindirs_sort()
 
 export LC_COLLATE=C
 
-COMMAND="$1"
-KERNEL_VERSION="$2"
-KERNEL_IMAGE="$3"
+if [[ "${0##*/}" == 'installkernel' ]]; then
+    COMMAND='add'
+else
+    COMMAND="$1"
+    shift
+fi
+
+KERNEL_VERSION="$1"
+KERNEL_IMAGE="$2"
 
 if [[ -f /etc/machine-id ]]; then
     read MACHINE_ID < /etc/machine-id