Security Hardening: Remove macro substitution support from system hook shell exec command (was undocumented anyway).

Author: jhuckaby

lib/action.js

@@ -1250,7 +1250,7 @@ class Actions {
 
 			if (hook.shell_exec) {
 				// allow placeholder subs on command
-				var cmd = this.messageSub( hook.shell_exec, data );
+				var cmd = hook.shell_exec;
 				var child_opts = {
 					cwd: os.tmpdir(),
 					env: Object.assign( {}, this.cleanEnv(), { XYOPS: this.server.__version } ),