LU-930 misc: improve .mailmap coverage

LU-930 misc: improve .mailmap coverage

Improve .mailmap coverage and correctness for "git shortlog"
and related commands.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I41a2474f2c69e1e49b5f8569ca6cc7bfcf3ebbe5
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/47894
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Elena Gryaznova <elena.gryaznova@hpe.com>
Reviewed-by: Peter Jones <pjones@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>