Fix race condition during start:dev

There's no way to run `aragon devchain` that makes it return to the
terminal with the chain running in the background. Since it never
returns, there's no good & quick way to run these two commands
back-to-back. Instead, this gets around the problem most of the time by
giving the devchain ten seconds to start up before continuing.

apps/shared/test-helpers/ganache-cli.sh

@@ -38,6 +38,7 @@ start_testrpc() {
 		aragon devchain --reset --port "$testrpc_port" &
 	elif [ "$DEV" = true ]; then
 		aragon devchain --reset --port "$testrpc_port" &
+		sleep 10 # wait for devchain to start TODO: modify cli to return rather than require interruption
 		npm run frontend &
 	elif [ "$NO_CLIENT" = true ]; then
 		aragon devchain --reset --port "$testrpc_port" &