Fix maxNoDamageTicks being cut in half

[jedediah]

For no apparent reason, noDamageTicks was counting down from maxNoDamageTicks to maxNoDamageTicks/2. Both of these values can be set through the Bukkit API, but there is no correction for this strange offset. As a result, the value passed to setMaxNoDamageTicks would effectively be cut in half, and the value passed to setNoDamageTicks would be reduced by maxNoDamageTicks/2.

[tonybruess]

Missing two // CraftBukkit comments

[jedediah]

added comments

[ttaylorr]

Looks good to merge

[tonybruess]

One thing. Bukkit/CraftBukkit@bccc961ddf29fa2c9463e5648fc425a78fa4a7b5 changed the damage API and mentioned the changes affecting noDamageTicks. Not sure exactly what they did, but would it be better to update SportBukkit? I updated it a while ago but it caused issues with our kill tracking.