conf: Reset disk type if <source> element is completely missing

The disk type is not part of source and thus it's parsed earlier. This
bypasses the checks when parsing a disk type='network' if it's
completely missing the source.

Since there are possible active users of this (it was reported as a
problem with openstack) fix it by resetting the disk type to '_FILE' for
an empty cdrom which is handled correctly.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

src/conf/domain_conf.c

@@ -10126,6 +10126,10 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
         }
     }
 
+    /* Reset def->src->type in case when 'source' was not present */
+    if (!source)
+        def->src->type = VIR_STORAGE_TYPE_FILE;
+
     /* Only CDROM and Floppy devices are allowed missing source path
      * to indicate no media present. LUN is for raw access CD-ROMs
      * that are not attached to a physical device presently */

tests/qemuxml2xmloutdata/disk-source-pool.xml

@@ -25,7 +25,7 @@
       <readonly/>
       <address type='drive' controller='0' bus='0' target='0' unit='1'/>
     </disk>
-    <disk type='volume' device='cdrom'>
+    <disk type='file' device='cdrom'>
       <driver name='qemu' type='raw'/>
       <target dev='hdc' bus='ide'/>
       <readonly/>