LU-12479 utils: cleanup gcc8 string warnings

LU-12479 utils: cleanup gcc8 string warnings

Cleanup some trivial buffer overflows

This patch is back-ported from the following one:
Lustre-commit: 164434eed2161337000257968e37d2714e9c9599
Lustre-change: https://review.whamcloud.com/35354

Test-Parameters: trivial
Cray-bug-id: LUS-6962
Signed-off-by: Shaun Tancheff <stancheff@cray.com>
Change-Id: I17dd1d042c4050e351aca856931ce1107fd5b08f
Reviewed-on: https://review.whamcloud.com/35586
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>