tests: fix virt-xml test

Broken by commit b1c0a1c.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>

tests/clitest.py

@@ -885,7 +885,7 @@ def add_compare(self, cat, args, compfile, **kwargs):
 
 c = vixml.add_category("edit clear", "test-for-virtxml --print-diff --define", compare_check="1.2.2")  # compare_check=input type=keyboard output
 c.add_invalid("--edit --memory 200,clearxml=yes")  # clear isn't wired up for memory
-c.add_compare("--edit --disk path=/foo/bar,target=fda,bus=fdc,device=floppy,clearxml=yes", "edit-clear-disk")
+c.add_compare("--edit --disk path=/foo/bar,size=2,target=fda,bus=fdc,device=floppy,clearxml=yes", "edit-clear-disk")
 c.add_compare("--edit --cpu host-passthrough,clearxml=yes", "edit-clear-cpu")
 c.add_compare("--edit --clock offset=utc,clearxml=yes", "edit-clear-clock")
 c.add_compare("--edit --video clearxml=yes,model=virtio,accel3d=yes", "edit-video-virtio")