model validate can't get all parameters from operation in function validateRequest

In function validateRequest, model validate can only get parameters under request methods, public parameters will be missed

For example:
``` json
"paths": {
"(path)": {
"parameters": [A, B, C]
"put": {
"parameters": [D]
}
}
}
```
In this example, function validateRequest can only validate parameter-D
then will report error OBJECT_MISSING_REQUIRED_PROPERTY for parameter-A, parameter-B and parameter-C