LU-13543 lustre: update *pos in seq_file .next functions

LU-13543 lustre: update *pos in seq_file .next functions

Patch fixes mdt_hsm_actions_debugfs seq operations to work with
new seq file logic in newer kernels

Meanwhile it finishes remaining work originating in LU-13985 which
updates ->next functions to always increment *pos as it is expected
by kernel

Test-Parameters: clientdistro=el8.2 serverdistro=el8.2 testlist=sanity-hsm
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: I4f077b633fbf7d420bfda10cce6b0141cef07761
Reviewed-on: https://review.whamcloud.com/40757
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Neil Brown <neilb@suse.de>