Description of problem:
Use command 'vol-create' with the Vol XML to create a volume,but it will failed with error: "command 'vol-create' requires <file> option"

Version-Release number of selected component (if applicable):
libvirt-0.8.7-14.el6.x86_64
qemu-img-0.12.1.2-2.152.el6.x86_64
qemu-kvm-0.12.1.2-2.152.el6.x86_64
kernel-2.6.32-125.el6.x86_64

How reproducible:
5/5

Steps to Reproduce:
1.Setup a pool of directory type with that xml.
<pool type='dir'>
  <name>dir_pool</name>
  <uuid>70a7eb15-6c34-ee9c-bf57-69e8e5ff3fb2</uuid>
  <capacity>0</capacity>
  <allocation>0</allocation>
  <available>0</available>
  <source>
  </source>
  <target>
    <path>/var/lib/libvirt/images</path>
    <permissions>
      <mode>0700</mode>
      <owner>0</owner>
      <group>0</group>
      <label>some_label_t</label>
    </permissions>
  </target>
</pool>

# virsh pool-define dir_pool.xml

# virsh pool-start dir_pool
Pool dir_pool started

2. Create a raw vol

#cat raw.xml
<volume>
  <name>raw.img</name>
  <source>
 </source>
  <capacity>22300000</capacity>
  <allocation>22300000</allocation>
  <target>
    <path>/var/lib/libvirt/images/raw.img</path>
<format type='raw'/>
  </target>
</volume>

# virsh vol-create --pool dir_pool raw.xml 
error: command 'vol-create' requires <file> option

  
Actual results:
Use command 'vol-create' with the Vol XML to create a volume,but it will failed with error: "command 'vol-create' requires <file> option"

Expected results:
Volume should be created successfully

Additional info:

1.If add option "--file" vol created will be successful.

# virsh vol-create --pool dir_pool --file col.xml 
Vol raw.img created from col.xml

2.Or if delete option "--pool" vol created will be successful.

# virsh vol-create  dir_pool col.xml 
Vol raw.img created from col.xml