LU-11621 utils: optimize lhsmtool_posix with copy_file_range()

LU-11621 utils: optimize lhsmtool_posix with copy_file_range()

Newer kernels and glibc offer copy_file_range() which avoids
a context switch needed with read() + write() for file data
copying. In the future Lustre can look to optimize this copy
on the server backend. Update lhsmtool_posix to use this new
functionality.

Change-Id: If63d57b89902f3d5c9ddde66901f3f55d15080f5
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/38651
Reviewed-by: Ben Evans <beevans@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>