Unit tests for Mellanox deployment serializers

1. Added unit tests for Mellanox changes in deployment serializers.
2. Fixed conventions of python string formatting.

Closes-bug: #1343355

Change-Id: I33c7fd5b69b096de808cb8cabccaf6f6056f8508
Signed-off-by: Aviram Bar-Haim <aviramb@mellanox.com>
Merge "Unit tests for Mellanox deployment serializers"