Make sure argv indeces exist before comparing them in test_lfs.c and test_time.c

[amberjennings]

This should resolve issue #89

• Ensures that argv values exist before attempting to strcmp them to operations
• This is far from a perfect solution -- in the future, it would be good to have this checking happen before anything else is done.

[ryanpdx]

With #99 are we dropping support for F4 apps, so this is no longer needed