qemu: Do not start with source for removable disks if tray is open

This is similiar with physical world, one will be surprised if the
box starts with medium exists while the tray is open.

New tests are added, tests disk-{cdrom,floppy}-tray are for the qemu
supports "-device" flag, and disk-{cdrom,floppy}-no-device-cap are
for old qemu, i.e. which doesn't support "-device" flag.

tests/qemuxml2argvdata/qemuxml2argv-disk-floppy-tray.args

@@ -0,0 +1,10 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test \
+/usr/bin/qemu -S -M pc -m 214 -smp 1 -nographic -nodefaults \
+-monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
+-drive file=/dev/HostVG/QEMUGuest1,if=none,id=drive-ide0-0-0 \
+-device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
+-drive file=/dev/fd0,if=none,id=drive-fdc0-0-0 \
+-global isa-fdc.driveA=drive-fdc0-0-0 \
+-drive if=none,id=drive-fdc0-0-1 \
+-global isa-fdc.driveB=drive-fdc0-0-1 \
+-usb -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3