Add ostree=aboot for signed Android Boot Images #2844

Some kernel images are delivered in a signed kernel + cmdline + initramfs + dtb blob. When this is added to the commit server side, only after this do you know what the cmdline is, this creates a recursion issue. To avoid this, in the case where we have ostree=aboot karg set, do the bls parsing in the initramfs instead, so we can take advantage of existing bls logic.