LU-12580 lov: fix typo in lov_comp_md_size

If the component of a PFL file is not initialized,
we should use 0 as the stripe size when calculating
the LOVEA size.

Change-Id: I4ff5f4a78bc1d432cc1ac6fa3733461bd6b762e6
Fixes: 62f64a1077 ("LU-9489 lod: keep minimum LOVEA size")
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-on: https://review.whamcloud.com/37493
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>