Fixed reference

I cannot understand why, but apparently there was a micture of COLVAR
and forces in the forces.reference file... Fixed now.

regtest/rt8/forces.reference

-#! FIELDS time parameter d2
- 0.000000   -5.3692069002
- 0.050000   -5.3890475142
- 0.100000   -5.4557149798
- 0.150000   -5.4313735807
- 0.200000   -5.3033063121
-.262993  -0.175622
+108
+  9.431767   3.464885   1.545095
+X   0.433907   0.262993  -0.175622
+X   0.433907   0.262993  -0.175622
+X   0.433907   0.262993  -0.175622
+X   0.433907   0.262993  -0.175622
 X   0.433907   0.262993  -0.175622
 X   0.433907   0.262993  -0.175622
 X   0.433907   0.262993  -0.175622