storage: Fix the use-after-free memory bug
storage: Fix the use-after-free memory bug

https://bugzilla.redhat.com/show_bug.cgi?id=965442

Introduced by commit e0139e30444. virStorageVolDefFree free'ed the
pointers that are still used by the added volume object, this changes
it back to VIR_FREE.
(cherry picked from commit 4140dbedd9d2733b2beb1fda0878ad742f1122d2)

mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2,mithleshvrts/libvirt-0.10.2