LU-16152 utils: fix integer overflow in cYAML parser

LU-16152 utils: fix integer overflow in cYAML parser

Convert double to int64 correctly in cYAML parser.

Signed-off-by: Lei Feng <flei@whamcloud.com>
Test-Parameters: trivial testlist=sanity env=ONLY=65p
Change-Id: Ia3fd515c76ebfe6e5181301f53c702ef82056eba
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48649
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>