[ LSTM ] Add More Unit Test Cases

[ LSTM ] Add More Unit Test Cases

This Commit inclues,
 . Additional unittest
   - with return sequneces
   - with multiple batch size
   - with multiple batch + return sequences
   - with multiple batch + return sequences + multi-iteration
 . Fixed initialization bug during training
 . Remove check for tensor dot product to support multi-dimension
 tensor.

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

Signed-off-by: jijoong.moon <jijoong.moon@samsung.com>