FIX: Fail to remove the logical volume

The logical volume can not be removed when delete VM error. I look at the
code, found that parameter is a list in the libvirt's lvm, but in
imagebackend, parameters passed is a string.

Change-Id: I222f6c5cfe5be63105f2fd8afd7ccd209ca2e5f7
Closes-Bug: #1358552
Merge "FIX: Fail to remove the logical volume"