fix syntax error in utility functions used by create_ami

lib/vm.js

@@ -59,7 +59,7 @@ exports.list = function(cb) {
 // given something the user typed in, try to figure out what instance they're talking about
 function findInstance(r, name) {
   // is what the human typed in an instance id?
-  var x = jsel.match('object:has(:root > .instanceId:val("?"))', [ name ], r);
+  var x = jsel.match('object:has(:root > .instanceId:val(?))', [ name ], r);
   if (x.length) return x[0];
 
   // is what the human typed in the vm "short name" ?