warning messages are included on json data when is used json stdout_callback

[apenella]

Which ansible version are you using?
ansible 2.10.5
config file = ??/.ansible.cfg
configured module search path = ['??/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
ansible python module location = ??/.local/lib/python3.8/site-packages/ansible
executable location = ??/.local/bin/ansible
python version = 3.8.5 (default, Jul 28 2020, 12:59:40) [GCC 9.3.0]

Which go version are you using?
go version go1.15.6 linux/amd64

Which go-ansbile version are you using?
0.7.0

What did you see?
When is run a playbook using the json stdout_callbak, and there is a warning message on the output (with warning messages I mean those messages that start with [WARNING]), that message is included on json data and then the parsing done by JSONParse fails.

exit status 4                                                                                  
panic: Unmarshall error                     
        invalid character '[' after top-level value

On the other hand, some warning messages returned by ansible-playbook in one line on terminal are seen as multiple line messages by go-ansible

Thats an example:

• Shell output:

$ ANSIBLE_STDOUT_CALLBACK=json ansible-playbook  --inventory 127.0.0.1,  --user apenella site.yml
[WARNING]: Unhandled error in Python interpreter discovery for host 127.0.0.1: Failed to connect to the host via ssh: ssh: connect to host 127.0.0.1 port 22: Connection refused
...

• go-ansible output:

-- #[WARNING]: Unhandled error in Python interpreter discovery for host 127.0.0.1:#
-- #Failed to connect to the host via ssh: ssh: connect to host 127.0.0.1 port 22:#
-- #Connection refused#

How to reproduce the issue?
To reproduce the issue I used simple-ansibleplaybook-json example.
I forced a connection error updating ansiblePlaybookConnectionOptions definition as is shown below:

	ansiblePlaybookConnectionOptions := &ansibler.AnsiblePlaybookConnectionOptions{
	//	Connection: "local",
		User:       "apenella",
	}

You could see the scanned text by go-ansible updating ansiblePlaybookJSONResults as is shown below:

	for scanner.Scan() {
		line := scanner.Text()
		if !skipLine(line) {
                        // println for debuggin purpose
                        fmt.Println("-- #" + line + "#")
			fmt.Fprintf(w, "%s", line)
		}
	}

The issue is related to #23

[apenella]

On DefaultExecutor is created a multireader for stdout and stderr, then the stdout and stderr output is written on same writer and that causes an invalid json outcome when there is a warning message during playbook execution.

Here there is where is defined the multireader:
https://github.com/apenella/go-ansible/blob/master/execute/defaultExecute.go#L85

I am going to separete stdout and stderr to avoid this kind of errors.