Wall mounted blocks sometimes pop off when placed by structure module

[mitchts]

Structures that contain wall mounted blocks (only tested with ladders and signs) will sometimes have them pop off the wall when placed.

Example structure in mapdev:

Upon cycling to the map there are already items on the ground (note that these will drop regardless of whether the item is on item remove):

When the structure is placed:

The ones which pop off appear to be consistent between matches. Once placed more dropped items are created in addition to the ones already dropped on match cycle.

Demo map: ladder_struct_demo.zip

[Pablete1234]

Using update="false" in the <dynamic> should fix this
See #1419