Inconsistent request types in waitFor().http() and waitFor().execution().action()

**Citrus Version**
2.7.8

**Expected behavior**
When I wait for a http server via `waitFor().http()` and `waitFor().execution().action()`, I expect them to request the server with the same http request method.

**Actual behavior**
```java
waitFor()
.execution()
.action(send(server))
```
requests with `POST`

```java
waitFor()
.http()
.url(server)
```
requests with `HEAD`

**Test case sample**
Both tests turn green, while expecting different HTTP methods on the server side.

*These tests can be found in the file `WaitTestRunnerIT` after #547 has been merged. Until then: e45e1071dbce485a0f5a13e863cfae751978d120*
```java
@CitrusTest
public void waitHttpAsAction() {

//GIVEN
String server = String.format("http://localhost:%s", serverPort);
httpServer.setPort(serverPort);
start(httpServer);

parallel().actions(
sequential().actions(
//WHEN
waitFor()
.execution()
.action(send(http -> http.endpoint(server)))
),
sequential().actions(
//THEN
http(http -> http.server(httpServer).receive().post()),
http(http -> http.server(httpServer).respond(HttpStatus.NOT_FOUND)),
http(http -> http.server(httpServer).receive().post()),
http(http -> http.server(httpServer).respond(HttpStatus.OK))
)
);

doFinally().actions(stop(httpServer));
}

@CitrusTest
public void waitHttp() {

//GIVEN
String server = String.format("http://localhost:%s", serverPort);
httpServer.setPort(serverPort);
start(httpServer);

parallel().actions(
sequential().actions(
//WHEN
waitFor()
.http()
.url(server)
),
sequential().actions(
//THEN
http(http -> http.server(httpServer).receive().head()),
http(http -> http.server(httpServer).respond(HttpStatus.NOT_FOUND)),
http(http -> http.server(httpServer).receive().head()),
http(http -> http.server(httpServer).respond(HttpStatus.OK))
)
);

doFinally().actions(stop(httpServer));
}
```

Start with the WaitTestRunnerIT tests described in the issue, using commit e45e1071dbce485a0f5a13e863cfae751978d120 if #547 is not merged. Compare the requests produced by waitFor().http() and waitFor().execution().action(send(...)), then run the two test cases. Done means both paths use the same HTTP request method and the server-side expectations pass.

Written by the indexing model from the issue text.