Fixed memory leak in vicNl.c.

This fixes issue #115.

The fix was simply to move some "free" statements in vicNl.c to outside of an OUTPUT_FORCE "if" block.

I tested this on the pnw test cells, for the following cases, confirming that the output is identical to 4.1.2.k:
1. 24hwb, OUTPUT_FORCE=FALSE
2. 1heb, OUTPUT_FORCE=TRUE.
I ran valgrind -v --leak-check=full for these cases to confirm that the memory leaks were gone.