LU-14268 lod: fix layout generation inc for mirror split

LU-14268 lod: fix layout generation inc for mirror split

Mirror split does not increase the layout generation properly.

Mirror split does not change FLR state of the file, even when it
contains 1 mirror afterwards, and FLR state should be LCM_FL_NONE
instead.

Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Change-Id: I9c9621d67d901f2e9ca6ed3e0684cd308c396076
Reviewed-on: https://review.whamcloud.com/41068
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>