Fix alignment of -H output

[spook]

Output can be misaligned a bit with --human-readable (-H) output.

Example:

# bin/sshping -H aspen.example.com
ssh-Login-Time:               2.44  s   <-- extra space
Minimum-Latency:               885 us
Median-Latency:               1.06 ms
Average-Latency:              1.13 ms
Average-Deviation:             294 us
Maximum-Latency:              5.40 ms
Echo-Count:                  1.00 kB   <-- Skewed by one here and down
Upload-Size:                 8.00 MB
Upload-Rate:                 6.83 MB/s
Download-Size:               8.00 MB
Download-Rate:               5.23 MB/s