Error on generating slug for three or more products with same name

[lruozzi9]

There is a BUG in ImmutableSlugValueHandler on generating slug for a product with the same name as another.
For example:
If I have three products named "T-shirt banana", the importer will generate a "t-shirt-banana" slug for the first one, "t-shirt-banana-1" for the second one, and "t-shirt-banana-1-2" for the third instead of "t-shirt-banana-2".