From commit id 'd53bbfd1'

Found one core and one possible memory leak. Core seen during local
virt-test/tp_libvirt run for the vol_create_from test. The memory leak
was seen by inspection during a review of all VIR_APPEND_ELEMENT changes

In storage_backend_disk/virStorageBackendDiskMakeDataVol(), the 'vol'
needs to be kept around since it's used later, so use the _COPY macro.
This caused a segv in libvirtd:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffe87c3700 (LWP 6919)]
virStorageBackendDiskMakeDataVol (vol=0x0, groups=0x7fffc8000d70, pool=0x7fffc8002460) at storage/storage_backend_disk.c:66
66          if (vol->target.path == NULL) {

In storage_backend_rbd/virStorageBackendRBDRefreshPool() there's a failure
path where the 'vol' needs to go through virStorageVolDefFree() since it
wouldn't be appended.