Fix crush shutdown when MITM has it's own loop (#5042)
Fix crush shutdown when MITM has it's own loop (#5042)

When I call shutdown with a different loop in the current thread from MITM loop, it's crashes with the error:
`ValueError: The future belongs to a different loop than the one specified as the loop argument`

Setting a loop explicit fixes the problem.
mhils/mitmproxy,mitmproxy/mitmproxy,mitmproxy/mitmproxy,mhils/mitmproxy,mhils/mitmproxy,mhils/mitmproxy,mhils/mitmproxy,mitmproxy/mitmproxy,mitmproxy/mitmproxy,mitmproxy/mitmproxy