do not add disk cache mode from an empty string (apache#12248)

Co-authored-by: Daan Hoogland <dahn@apache.org>

Author: 2 people

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtDomainXMLParser.java

@@ -111,7 +111,9 @@ public boolean parseDomainXML(String domXML) {
                     def.defNetworkBasedDisk(diskPath, host, port, authUserName, poolUuid, diskLabel,
                         DiskDef.DiskBus.valueOf(bus.toUpperCase()),
                         DiskDef.DiskProtocol.valueOf(protocol.toUpperCase()), fmt);
-                    def.setCacheMode(DiskDef.DiskCacheMode.valueOf(diskCacheMode.toUpperCase()));
+                    if (StringUtils.isNotBlank(diskCacheMode)) {
+                        def.setCacheMode(DiskDef.DiskCacheMode.valueOf(diskCacheMode.toUpperCase()));
+                    }
                 } else {
                     String diskFmtType = getAttrValue("driver", "type", disk);
                     String diskCacheMode = getAttrValue("driver", "cache", disk);