Add trivial function nxtask_uninit(). This function will undo all operations on a TCB performed by task_init() and release the TCB by calling kmm_free(). This is intended primarily to support error recovery operations after a successful call to task_init() such was when a subsequent call to task_activate fails.
That error recovery is trivial but not obvious. This helper function should eliminate confusion about what to do to recover after calling nxtask_init()