Correct types of int16 and int8 input tensors for tests

Fixes input tensors for int16 and int8 tests for MUL,
LOGICAL_LEFT/RIGHT_SHIFT, COND_IF, WHILE_LOOP

Change tensor generator functions to use type aware
randTensor() function.

Signed-off-by: Jeremy Johnson <jeremy.johnson@arm.com>
Change-Id: If81a783929c29e1fd5e91477dbcdaf79c738f6b0