[ unittest ] Remove unproperly formulated TCs

- unittest_nntrainer_modelfile have not been initialized properly, and fixing this issue shown multiple failing TCS.
- Temporally remove TCs, and upcoming commit will introduce them

**Self evaluation:**
1. Build test:     [X]Passed [ ]Failed [ ]Skipped
2. Run test:     [X]Passed [ ]Failed [ ]Skipped

Signed-off-by: skykongkong8 <ss.kong@samsung.com>