WASHINGTON — Government contracting giant General Dynamics announced Monday that it is buying CSRA, a government IT services conglomerate that formed in 2015 amid a wave of industry consolidation. The $9.6 billion deal includes $6.8 billion cash and $2.8 billion debt. General Dynamics will buy all shares of CSRA for $40.75 under the terms of the deal, a 32 percent premium from Friday’s closing price.