## 🐛 Bug Report

I cannot retrieve the firefox console logs, I get the following JsonException when I try to do so:
```
Exception in thread "main" org.openqa.selenium.json.JsonException: Unable to determine type from: H. Last 1 characters read: H
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:17:03'
System info: host: 'vivat', ip: '127.0.0.1', os.name: 'Linux', os.arch: 'amd64', os.version: '5.3.10-arch1-1', java.version: '1.8.0_232'
Driver info: driver.version: RemoteWebDriver
	at org.openqa.selenium.json.JsonInput.peek(JsonInput.java:122)
	at org.openqa.selenium.json.JsonTypeCoercer.lambda$null$6(JsonTypeCoercer.java:140)
	at org.openqa.selenium.json.JsonTypeCoercer.coerce(JsonTypeCoercer.java:126)
	at org.openqa.selenium.json.Json.toType(Json.java:69)
	at org.openqa.selenium.json.Json.toType(Json.java:55)
	at org.openqa.selenium.json.Json.toType(Json.java:50)
	at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:87)
	at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:49)
	at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:158)
	at org.openqa.selenium.remote.service.DriverCommandExecutor.execute(DriverCommandExecutor.java:83)
	at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:552)
	at org.openqa.selenium.remote.RemoteExecuteMethod.execute(RemoteExecuteMethod.java:35)
	at org.openqa.selenium.remote.RemoteLogs.getRemoteEntries(RemoteLogs.java:81)
	at org.openqa.selenium.remote.RemoteLogs.get(RemoteLogs.java:77)

```

After debugging on W3CHttpResponseCode#decode, it seems that the exception is thrown because the content of the response is not a JSON but a text/plain that only contains "HTTP method not allowed". 

When checking what request has been sent, it seems that the following POST request is performed:
> POST /session/81a0b1fc-cc58-468e-9976-3d783c18f1db/log

So I guess there is two issues:
  - the command is wrong for Firefox
  - the error is not parsed correctly

I don't reproduce on Chrome, only on Firefox.

## To Reproduce

Here's the Java method I'm using to reproduce:

```
// GeckoDriver v0.26.0
System.setProperty("webdriver.gecko.driver", "/home/urli/geckodriver/geckodriver");
FirefoxOptions firefoxOptions = new FirefoxOptions();
LoggingPreferences logPrefs = new LoggingPreferences();
logPrefs.enable(LogType.BROWSER, Level.ALL);

firefoxOptions.setCapability(CapabilityType.LOGGING_PREFS, logPrefs);

WebDriver driver = new FirefoxDriver(firefoxOptions);
driver.get("https://developer.mozilla.org/fr/docs/Web/API/console");
for (LogEntry logEntry : driver.manage().logs().get(LogType.BROWSER)) {
   System.out.println(String.format("[%s] [%s]", logEntry.getLevel(), logEntry.getMessage()));
}
driver.quit();
```

Detailed steps to reproduce the behavior:

## Expected behavior

I expect to see the browser console logs.

## Environment

OS: ArchLinux
Browser: Firefox
Browser version: 70.0.1
Browser Driver version: GeckoDriver 0.26.0
Language Bindings version: Java 3.141.59

response.getState() :
          errorCodes.toState(response.getStatus()));
      exception.put("message", ((WebDriverException) value).getMessage());
      exception.put("stacktrace", Throwables.getStackTraceAsString((WebDriverException) value));
      if (value instanceof UnhandledAlertException) {
        HashMap<String, Object> data = new HashMap<>();
        data.put("text", ((UnhandledAlertException) value).getAlertText());
        exception.put("data", data);
      }
      value = exception;
    }
    toReturn.put("value", value);
    return toReturn;
  }
  @Override
  protected Response reconstructValue(Response response) {
    response.setValue(elementConverter.apply(response.getValue()));
    return response;
  }
  private WebDriverException createException(String error, String message) {
    Class<? extends WebDriverException> clazz = errorCodes.getExceptionType(error);
    try {
      Constructor<? extends WebDriverException> constructor = clazz.getConstructor(String.class);
      return constructor.newInstance(message);
    } catch (ReflectiveOperationException e) {
      throw new WebDriverException(message);
    }
  }
}