LU-13985 lustre: seq_file .next functions must update *pos

LU-13985 lustre: seq_file .next functions must update *pos

A seq_file .next function must update *pos on EOF to a value which
will cause a subsequent ->start to also return EOF.
If it doesn't the last record of the file can be returned
twice to a 'read()'.  Also the seq_file code will generate
a warning.

This patch fixes various ->next functions to always update
*pos.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Ia0c432cd50550ecde6b308cbc554b316fa03adae
Reviewed-on: https://review.whamcloud.com/40035
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>