By Lisa Baertlein LONG BEACH, Calif., Feb 28 (Reuters) – The former Amazon.com Inc executive who oversaw the e-commerce company’s transportation network buildout for its sellers, now aims to do the same for rival shipping customers as chief executive of logistics startup Flexport. “I wanted to … do it again for everyone else,” said Dave Clark, the former Amazon executive who will become Flexport CEO on March 1 after spending six months as co-CEO. Getting big is the key to success, Clark said at S&P Global Market Intelligence’s TPM23 conference in Long Beach, California, on Tuesday. “Most companies will never have the opportunity to roll up the...