mv_machine_learning: fix memory leak issue

mv_machine_learning: fix memory leak issue

[Version] : 0.23.13
[Issue type] bug fix.

Fixed a memory leak issue with non-meta file inference by introducing
convertToFloat function of TensorBuffer class, which clears owner_is_backend
so that the buffer allocated with float type can be released properly.

And also this patch drops the code smell, code duplication, and
renames existing function name - setTensorBuffer to addTensorBuffer.

Change-Id: I062aa9cf05fc6ebb53e4cfd0c4ae6bb0d98d65fe
Signed-off-by: Inki Dae <inki.dae@samsung.com>