Changes previous MP5 to the current M4 coaxial.
Pulls random tankbot spawns.  There was much rejoicing.
Revert "Pulls random tankbot spawns.  There was much rejoicing."

This reverts commit eb29f38eb6c0551371459be088ede218ab5c3f4a.

Reinstates tankbot spawn.

I'm disabling the cannon against folks on foot.
Ensures that the tankbot is awful hesitant to use its primary: you've got to be in range and sufficently large or Friendly to get the 120mm as an option.
Tightens the 120mm HEAT blast radius, hopefully enhancing survivability and "believability".

In practice, I'm pretty confident that standing within 5 meters of a HEAT impact would seriously injure or kill an EOD-suited human--enough that I wouldn't volunteer to test the theory.  But wev.
Force the tankbot primary to take longer to lock, and not retain lock between shots.

Between all of these, it's possible for it to miss enough to survive the first shot.  Generally you won't be in very good shape and actually doing something in time is unlikely, but you don't get one-shotted.
Updates relevant tag documentation.
Merge pull request #9970 from KA101/tankfix

Tankbot fix & pull