UnderConstructionLoop event can start multiple instances on the same scaffold

[xezon]

• Is related to #2145

The UnderConstructionLoop event can start multiple instances on the same scaffold.

Repro:

• Start construction
• Stop the Dozer
• Continue construction

2 construction loops will play now.

The audio event limit is 2, so there will be only a maximum of 2 stacked events.

AudioEvent UnderConstructionLoop
  Control = loop all random
  Sounds      = gconlo2a gconlo2b gconlo2c gconlo2d gconlo2e gconlo2f
  Attack      = gconlo1a
  Decay       = gconlo3a
  Priority = lowest
  Limit = 2
  MinRange = 100
  MaxRange = 1000
  VolumeShift = -10
  Volume = 80
  Type       = world shrouded everyone
End

[xezon]

I think the proper fix here is to stop the construction audio when the builder stops constructing. Right now the construction sound will continue, even if the scaffold is not progressing.