exec init.sh from init.rc itself

I wasn't happy with standard method of packing two separate (compressed) ramdisks into a single initrd. It caused unneccasary CPU overheads for decompressing stock ramdisk especially compressed ones and rewriting data to rootfs /. This commit improves upon it by having recovery.cpio (xz in this case) in /sbin of stock ramdisk itself and exec recovery init when keycheck is detected. Boot times also become relatively shorter.

Signed-off-by: Rachit Rawat <rachit.rc.rawat@gmail.com>