go/oasis-test-runner/cmd: Don't print error messages twice

Previously, Execute() called nodeCommon.EarlyLogAndExit() if there was
an error running rootCmd.Execute() which in turn printed the error to
stderr.
The error message is printed to stdout via github.com/spf13/cobra's
ExecuteC() already, so this resulted in the same error message being
printed twice.

go/oasis-test-runner/cmd/root.go

@@ -75,7 +75,7 @@ func RootCmd() *cobra.Command {
 // Execute spawns the main entry point after handing the config file.
 func Execute() {
 	if err := rootCmd.Execute(); err != nil {
-		nodeCommon.EarlyLogAndExit(err)
+		os.Exit(1)
 	}
 }