kernel-install: Remove existing initramfs if it's older than the kernel

Currently we fail to install a new kernel with "make install" on the second
try, because dracut won't over-write the initramfs without --force.  In this
patch, 20-grub.install will remove an existing initramfs if it's newer than the
kernel we're installing.

Resolves: rhbz#1638405
Signed-off-by: Peter Jones <pjones@redhat.com>

20-grub.install

@@ -114,6 +114,12 @@ case "$COMMAND" in
             fi
             grub2-editenv - set "saved_entry=${NEWDEFAULT}"
 
+            # this probably isn't the best place to do this, but it will do for now.
+            if [ -e "${BOOTPREFIX}${INITRD}" -a -e "${BOOTPREFIX}${LINUX}" -a \
+                 "${BOOTPREFIX}${INITRD}" -ot "${BOOTPREFIX}${LINUX}" -a \
+                 -x /usr/lib/kernel/install.d/50-dracut.install ]; then
+                rm -f "${BOOTPREFIX}${INITRD}"
+            fi
             exit 0
         fi