Revert "initramfs-live-install*: fix the "install" boot option"

This was not the correct fix for this issues, it turns out that
base-files package was getting installed un-intentionally when
rpm-postinsts was split out. The base-files recipe lays down the
link that caused the cat failure.

[YOCTO #4504]

This reverts commit 45e460d084.

(From OE-Core rev: 7d50133dd5c955d97193cc26458ebbf84dbfe0a4)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/initrdscripts/files/init-install.sh

@@ -78,6 +78,7 @@ if [ ! -b /dev/loop0 ] ; then
 fi
 
 mkdir -p /tmp
+cat /proc/mounts > /etc/mtab
 
 disk_size=$(parted /dev/${device} unit mb print | grep Disk | cut -d" " -f 3 | sed -e "s/MB//")