Fix for interctc test random failure
# What does this PR do ?

I finally figured out the reason for random failure of this test. It turns out that sometimes our input signal is such that for some models it results in all-zeros in the output of some initial encoder layers. This is then propagated all the way through the model and so the assert that final layer output is different from middle layer fails. After changing the code to pass processed signal directly, this should not happen anymore.

**Collection**: ASR

# Changelog 
- Add specific line by line info of high level changes in this PR.

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```python
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# Additional Information
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