qemu: capabilities: Always assume QEMU_CAPS_BOOTINDEX

The field was added in qemu v0.13.0-rc0-731-g1ca4d09ae0 so all supported
qemu versions now use it.

There's a LOT of test fallout as we did not use capabilities close
enough to upstream for many of our tests.

Several tests had a 'bootindex' variant. Since they'd become redundant
they are also removed here.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

tests/qemuxml2argvdata/luks-disks.args

@@ -22,7 +22,6 @@ path=/tmp/lib/domain--1-encryptdisk/monitor.sock,server,nowait \
 -rtc base=utc \
 -no-shutdown \
 -no-acpi \
--boot c \
 -usb \
 -object secret,id=virtio-disk0-luks-secret0,\
 data=9eao5F8qtkGt+seB1HYivWIxbtwUu6MQtg1zpj/oDtUsPr1q8wBYM91uEHCn6j/1,\
@@ -30,7 +29,7 @@ keyid=masterKey0,iv=AAECAwQFBgcICQoLDA0ODw==,format=base64 \
 -drive file=/storage/guest_disks/encryptdisk,\
 key-secret=virtio-disk0-luks-secret0,format=luks,if=none,id=drive-virtio-disk0 \
 -device virtio-blk-pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,\
-id=virtio-disk0 \
+id=virtio-disk0,bootindex=1 \
 -object secret,id=virtio-disk1-luks-secret0,\
 data=9eao5F8qtkGt+seB1HYivWIxbtwUu6MQtg1zpj/oDtUsPr1q8wBYM91uEHCn6j/1,\
 keyid=masterKey0,iv=AAECAwQFBgcICQoLDA0ODw==,format=base64 \