By Sarah N. Lynch WASHINGTON (Reuters) -The U.S. Federal Bureau of Investigation has wrested control of thousands of routers and firewall appliances away from Russian military hackers by hijacking the same infrastructure Moscow’s spies were using to communicate with the devices, U.S. officials said on Wednesday. An unsealed redacted affidavit described the unusual operation as a pre-emptive move to stop Russian hackers from mobilizing the compromised devices into a “botnet” – a network of hacked computers that can bombard other servers with rogue traffic. “Fortunately, we were able to disrupt …