Prior to this patch, DiskUsage() would calculate bytes available
by multiplying blocks available by block size in bytes:
disk.Avail = fs.Bavail * uint64(fs.Bsize)
Under some versions of Unix, fs.Bavail is of type uint64 and on
others (like FreeBSD) it is of type int64.
This causes a compile time error:
$ go build
# github.com/influxdata/influxdb/v2/pkg/fs
./fs_unix.go:81:25: invalid operation: fs.Bavail * uint64(fs.Bsize) (mismatched types int64 and uint64)
This patch type-converts fs.Bavail to unit64 to ensure that all
types in the expression align.
This prevents compile time errors under FreeBSD and other platforms
where fs.Bavail isn't uint64.
bd47d8efe1