tests: remove channel from TestTerminateSignal
tests: remove channel from TestTerminateSignal

It seems for some reason this channe causes a panic in TravisCI and it
doesn't look like it is necessary for the test to pass. Removing it
should prevent the panic.

joyent/containerpilot,tgross/containerbuddy,justenwalker/containerpilot,benoittoulme/containerpilot,benoittoulme/containerpilot,justenwalker/containerbuddy,benoittoulme/containerpilot,tgross/containerbuddy,joyent/containerpilot,flyinprogrammer/containerpilot,joyent/containerpilot,justenwalker/containerbuddy,joyent/containerbuddy,flyinprogrammer/containerpilot,joyent/containerbuddy,justenwalker/containerpilot