Charles Schwab's Joe Mazzola believes there's more going on than short covering in Wednesday's trading action after the U.S. and Iran agreed to a two-week ceasefire. That said, he warns investors that a reversal of headlines will lead markets to sell off once again. In the meantime, Joe says it gives more time for the Fed to "sit on their hands" for interest rates. He sees the earnings season being "fairly stable" despite the recent ramp of volatility.