HARARE (Reuters) - Former Zimbabwe finance minister Tendai Biti said on Thursday he would be happy to work in any national unity government that emerges from this week s coup, but only if opposition leader Morgan Tsvangirai was also on board.  If Morgan says he s in, I m in,  Biti, who earned international respect during his time as finance minister in a 2009-2013 unity government, told Reuters.  The country needs a solid pair of hands so one might not have a choice.  