virSecurityDACSetOwnershipInternal: Don't overwrite @path argument
virSecurityDACSetOwnershipInternal: Don't overwrite @path argument

As shown in the previous commit, @path can be NULL. However, in
that case @src->path is also NULL. Therefore, trying to "fix"
@path to be not NULL is not going to succeed. The real value of
NULLSTR() is in providing a non-NULL string for error reporting.
Well, that can be done in the error reporting without overwriting
argument.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

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