Corrected bugs in the unit tests that relied on old variables.

tests/test125cells.c

@@ -466,7 +466,6 @@ int main(int argc, char *argv[]) {
   /* Build the infrastructure */
   struct space space;
   space.periodic = 0;
-  space.h_max = h;
 
   struct phys_const prog_const;
   prog_const.const_newton_G = 1.f;

tests/test27cells.c

@@ -339,7 +339,6 @@ int main(int argc, char *argv[]) {
   /* Build the infrastructure */
   struct space space;
   space.periodic = 0;
-  space.h_max = h;
 
   struct engine engine;
   engine.s = &space;

tests/testPair.c

@@ -238,7 +238,6 @@ int main(int argc, char *argv[]) {
   }
 
   space.periodic = 0;
-  space.h_max = h;
 
   engine.s = &space;
   engine.time = 0.1f;

tests/testTimeIntegration.c

@@ -117,8 +117,6 @@ int main() {
     /* Kick... */
     runner_do_kick(&run, &c, 0);
 
-    /* Drift... */
-    runner_do_drift(&run, &c, 0);
   }
 
   /* Clean-up */