schema: Allow '0' offset for a <slice> of <disk>

Using slice to cut off the end of the image is a perfectly vaid
configuration. Use 'unsignedInt' instead of 'positiveInteger' for the
'offset' attribute in the XML schema and modify one test case to cover
this use case.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1960993
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>

docs/schemas/domaincommon.rng

@@ -1638,7 +1638,7 @@
 
   <define name="diskSourceSlice">
     <attribute name="offset">
-      <ref name="positiveInteger"/>
+      <ref name="unsignedInt"/>
     </attribute>
     <attribute name="size">
       <ref name="positiveInteger"/>

tests/qemuxml2argvdata/disk-slices.x86_64-latest.args

@@ -28,7 +28,7 @@ XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
 -boot strict=on \
 -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
 -blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/raw.img","node-name":"libvirt-6-storage","auto-read-only":true,"discard":"unmap"}' \
--blockdev '{"node-name":"libvirt-6-format","read-only":false,"driver":"raw","offset":1234,"size":321,"file":"libvirt-6-storage"}' \
+-blockdev '{"node-name":"libvirt-6-format","read-only":false,"driver":"raw","offset":0,"size":321,"file":"libvirt-6-storage"}' \
 -device virtio-blk-pci,bus=pci.0,addr=0x2,drive=libvirt-6-format,id=virtio-disk0,bootindex=1 \
 -blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/raw.img","node-name":"libvirt-5-storage","auto-read-only":true,"discard":"unmap"}' \
 -blockdev '{"driver":"raw","node-name":"libvirt-5-slice-sto","offset":9876,"size":123456789,"file":"libvirt-5-storage","auto-read-only":true,"discard":"unmap"}' \

tests/qemuxml2argvdata/disk-slices.xml

@@ -18,7 +18,7 @@
       <driver name='qemu' type='raw'/>
       <source file='/var/lib/libvirt/images/raw.img'>
         <slices>
-          <slice type='storage' offset='1234' size='321'/>
+          <slice type='storage' offset='0' size='321'/>
         </slices>
       </source>
       <backingStore/>

tests/qemuxml2xmloutdata/disk-slices.x86_64-latest.xml

@@ -21,7 +21,7 @@
       <driver name='qemu' type='raw'/>
       <source file='/var/lib/libvirt/images/raw.img'>
         <slices>
-          <slice type='storage' offset='1234' size='321'/>
+          <slice type='storage' offset='0' size='321'/>
         </slices>
       </source>
       <backingStore/>