Blender Git Loki

T76121 Driver depending on animated modifier property does not update

This fixes an issue where an animated modifier property that's used as
variable in a driver wouldn't animate that driver's value.

Building the relations for the driver target creates the relation
`PARAMETERS_EVAL` ? `DRIVER(variable)`. Building the relations for the
FCurve targeting the modifier property creates the relation
`ANIMATION_EXIT` ? `GEOMETRY_EVAL_INIT`.

This means that there is NOT a relation `ANIMATION_EXIT` ?
`PARAMETERS_EVAL`, and as a result, the driver is not properly updated
when its variable reads animated data. This is resolved in this commit
by adding the missing relation.

Differential Revision: https://developer.blender.org/D7615