qemuBackupBegin: Don't leak 'def' on early failures
qemuBackupBegin: Don't leak 'def' on early failures

The cleanup path expects that 'def' is assigned to 'priv->backup', but
that's not the case for early failures. Add a check to stop overwriting
of 'def' so that it can be freed.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

jardasgit/libvirt,crobinso/libvirt,jardasgit/libvirt,jardasgit/libvirt,jfehlig/libvirt,libvirt/libvirt,crobinso/libvirt,zippy2/libvirt,nertpinx/libvirt,jardasgit/libvirt,libvirt/libvirt,jfehlig/libvirt,libvirt/libvirt,zippy2/libvirt,jfehlig/libvirt,nertpinx/libvirt,olafhering/libvirt,jfehlig/libvirt,olafhering/libvirt,nertpinx/libvirt,zippy2/libvirt,olafhering/libvirt,zippy2/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt,olafhering/libvirt,nertpinx/libvirt,jardasgit/libvirt,crobinso/libvirt