Fix -Werror=reorder in random ray

[aprilnovak]

Description

MOOSE is compiled with -Werror=reorder, which checks for consistency in the ordering of variables in class definitions vs. when they are initialized in a constructor. Members are initialized in the order they are defined in the class, not the constructor, and using a different ordering can result in errors.

Alternatives

The easiest solution is to patch OpenMC, rather than change the compile flags in MOOSE.

Compatibility

No anticipated change.