Allow overwriting the name of the kvm executable

Export a KVM variable. This can be used to overwrite the executable for
the kvm command.

snf-image-host/common.sh.in

@@ -27,6 +27,7 @@ TIMEOUT="timeout"
 CURL="curl"
 TAR="tar"
 DATE="date -u" # Time in UTC
+KVM="kvm"
 
 # Temporary use stderr as monitoring file descriptor.
 # `create' will overwrite this

snf-image-host/defaults.in

@@ -84,6 +84,7 @@
 
 # Paths for needed programs. Uncomment and change the variables below if you
 # don't want to use the default one.
+# KVM="kvm"
 # LOSETUP="losetup"
 # KPARTX="kpartx"
 # SFDISK="sfdisk"

snf-image-host/kvm-common.sh

@@ -34,11 +34,11 @@ launch_helper() {
     set +e
 
     $TIMEOUT -k "$HELPER_HARD_TIMEOUT" "$HELPER_SOFT_TIMEOUT" \
-      kvm -runas "$HELPER_USER" -drive file="$HELPER_DIR/image",format=raw,if=virtio,readonly \
+      $KVM -runas "$HELPER_USER" -drive file="$HELPER_DIR/image",format=raw,if=virtio,readonly \
       -drive file="$blockdev",format=raw,if=virtio,cache=none -m "$HELPER_MEMORY" \
       -boot c -serial stdio -serial "file:$(printf "%q" "$result_file")" \
       -serial file:>(./helper-monitor.py ${MONITOR_FD}) \
-      -fda "$floppy" -vga none -nographic -parallel none -monitor null \
+      -drive file="$floppy",if=floppy -vga none -nographic -parallel none -monitor null \
       -kernel "$HELPER_DIR/kernel" -initrd "$HELPER_DIR/initrd" \
       -append "quiet ro root=/dev/vda1 console=ttyS0,9600n8 \
              hypervisor=$HYPERVISOR snf_image_activate_helper \