qemu: Add an ID to the qemu storage

While trying to test all possible qemu machine on LAVA, I found that
most cannot ran tests since they are stored on a qcow2 image.
This qcow2 image is then connected by any of IDE, SCSI, virtio
via this qemu option
"-drive format=qcow2,file=/var/lib/lava/dispatcher/tmp/jobid/apply-overlay-guest-49d_bpy5/lava-guest.qcow2,media=disk,if=XXXX"

But for some QEMU machine all thoses bus are not availlable.
For example the qemu ARM cubieboard does not have any of thoses.
After some research and discussion on #qemu, the only way to add the LAVA qemu
test storage on cubieboard is with:
"-device ide-hd,drive=lavatest"
where drive=id must be the same as the id present on "-drive"

So this patch adds such id on the "-drive" option.
This id could be tuned via a new "guestfs_driverid" option.

Signed-off-by: Neil Williams <neil.williams@linaro.org>
12 jobs from qemu_idtest in 9 minutes and 40 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
passed #24273
amd64
dispatcher-debian-10

00:03:08

passed #24271
amd64
dispatcher-debian-9

00:03:15

passed #24274
amd64
server-debian-10

00:02:52

passed #24272
amd64
server-debian-9

00:03:03

 
  Analyze
passed #24275
amd64
black

00:00:24

passed #24276
amd64
codestyle

00:00:31

passed #24277
dind amd64 allowed to fail
sast

00:01:43

 
  Build
passed #24280
amd64
amd64/pkg-debian-10

00:01:19

passed #24279
amd64
amd64/pkg-debian-9

00:01:29

passed #24278
amd64
doc

00:02:03

 
  Docker
passed #24281
dind amd64
amd64/lava-dispatcher

00:01:11

passed #24282
dind amd64
amd64/lava-server

00:02:35