I agree that the French sounding version is probably the most correct original pronunciation, but the harsher sounding pronunciation (more American English sounding) that many of us use has become so prevalent in the popular vernacular here that it appears to be considered somewhat official. If you look at the online Merriam Webster dictionary, they list both pronunciations. They even have recorded versions that you can listen to.

http://www.merriam-webster.com/dictionary/sabot