wic/filemap: Fall back to standard copy when no way to get the block map
For some filesystems, such as aufs which may be used by docker container,
don't support either the SEEK_DATA/HOLE or FIEMAP to get the block
map. So add a FileNobmap class to fall back to standard copy when there
is no way to get the block map.
[Yocto #12988]
Signed-off-by: Kevin Hao <kexin.hao@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
