zfs: fix storagepoolxml2xml test

Commit c4d27bdd dropped output of owner/group -1.

Update zfs tests accordingly.

tests/storagepoolxml2xmlout/pool-zfs-sourcedev.xml

@@ -12,8 +12,6 @@
     <path>/dev/zvol/testpool</path>
     <permissions>
       <mode>0755</mode>
-      <owner>-1</owner>
-      <group>-1</group>
     </permissions>
   </target>
 </pool>

tests/storagepoolxml2xmlout/pool-zfs.xml

@@ -11,8 +11,6 @@
     <path>/dev/zvol/testpool</path>
     <permissions>
       <mode>0755</mode>
-      <owner>-1</owner>
-      <group>-1</group>
     </permissions>
   </target>
 </pool>