add nocow test case

Add file in storagevolxml2xmlin and storagevolxml2xmlout, let
storagevolxml2xmltest and storagevolschematest cover 'nocow'.
Add test case to storagevolxml2argvtest to cover 'nocow'.
Signed-off-by: NChunyan Liu <cyliu@suse.com>

tests/storagevolxml2argvdata/qcow2-nocow-compat.argv

+qemu-img create -f qcow2 -b /dev/null \
+-o backing_fmt=raw,encryption=on,nocow=on,compat=0.10 \
+/var/lib/libvirt/images/OtherDemo.img 5242880K

tests/storagevolxml2argvdata/qcow2-nocow.argv

+qemu-img create -f qcow2 -b /dev/null \
+-o backing_fmt=raw,encryption=on,nocow=on \
+/var/lib/libvirt/images/OtherDemo.img 5242880K

tests/storagevolxml2argvtest.c

@@ -296,6 +296,12 @@ mymain(void)
     DO_TEST("pool-logical", "vol-logical",
             "pool-dir", "vol-qcow2-nobacking",
             "logical-from-qcow2", 0, FMT_COMPAT);
+    DO_TEST("pool-dir", "vol-qcow2-nocow",
+            NULL, NULL,
+            "qcow2-nocow", 0, FMT_OPTIONS);
+    DO_TEST("pool-dir", "vol-qcow2-nocow",
+            NULL, NULL,
+            "qcow2-nocow-compat", 0, FMT_COMPAT);
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }

tests/storagevolxml2xmlin/vol-qcow2-nocow.xml

+<volume>
+  <name>OtherDemo.img</name>
+  <key>/var/lib/libvirt/images/OtherDemo.img</key>
+  <source>
+  </source>
+  <capacity unit="G">5</capacity>
+  <allocation>294912</allocation>
+  <target>
+    <path>/var/lib/libvirt/images/OtherDemo.img</path>
+    <format type='qcow2'/>
+    <permissions>
+      <mode>0644</mode>
+      <owner>0</owner>
+      <group>0</group>
+      <label>unconfined_u:object_r:virt_image_t:s0</label>
+    </permissions>
+    <encryption format='qcow'>
+      <secret type='passphrase' uuid='e78d4b51-a2af-485f-b0f5-afca709a80f4'/>
+    </encryption>
+    <nocow/>
+  </target>
+  <backingStore>
+    <path>/dev/null</path>
+    <format type='raw'/>
+    <permissions>
+      <mode>0644</mode>
+      <owner>0</owner>
+      <group>0</group>
+      <label>unconfined_u:object_r:virt_image_t:s0</label>
+    </permissions>
+  </backingStore>
+</volume>

tests/storagevolxml2xmlout/vol-qcow2-nocow.xml

+<volume type='file'>
+  <name>OtherDemo.img</name>
+  <key>/var/lib/libvirt/images/OtherDemo.img</key>
+  <source>
+  </source>
+  <capacity unit='bytes'>5368709120</capacity>
+  <allocation unit='bytes'>294912</allocation>
+  <target>
+    <path>/var/lib/libvirt/images/OtherDemo.img</path>
+    <format type='qcow2'/>
+    <permissions>
+      <mode>0644</mode>
+      <owner>0</owner>
+      <group>0</group>
+      <label>unconfined_u:object_r:virt_image_t:s0</label>
+    </permissions>
+    <encryption format='qcow'>
+      <secret type='passphrase' uuid='e78d4b51-a2af-485f-b0f5-afca709a80f4'/>
+    </encryption>
+  </target>
+  <backingStore>
+    <path>/dev/null</path>
+    <format type='raw'/>
+    <permissions>
+      <mode>0644</mode>
+      <owner>0</owner>
+      <group>0</group>
+      <label>unconfined_u:object_r:virt_image_t:s0</label>
+    </permissions>
+  </backingStore>
+</volume>