Allow getting exit code without client.join after exhausting output

[erpadmin]

Bug reports

Steps to reproduce:
one example below, i've also ran a simple remote shell script with exit 1 call in it and the exit code is 0

from pssh.clients import ParallelSSHClient

host='myhost.localnet'
client = ParallelSSHClient([host], user=someuser)

output = client.run_command('bash -c \"exit 1\"')
for host, host_output in output.items():
    for line in host_output.stdout:
        print(line)

    stderr = ''.join(host_output.stderr)
    if stderr:
        print("STDERR: {}".format(stderr))

    retval = output[host].exit_code
    print("retval: {}".format(retval))

Expected behaviour: [What was expected to happen.]
retval should be 1
Actual behaviour: [What actually happened.]
retval is 0

[erpadmin]

interestingly this variant works as expected

from pssh.clients import ParallelSSHClient

host='myhost.localhost'
client = ParallelSSHClient([host], user='someuser')

output = client.run_command('bash -c \"exit 1\"')
client.join(output)

for host in output:
    retval = output[host].exit_code
    print("retval: {}".format(retval))

in the previous example my understanding is "Once either standard output is iterated on to completion, or client.join(output) is called, exit codes become available in host output. Iteration ends only when remote command has completed"

[erpadmin]

after fully iterating stdout, output[host].exit_code is not automatically updated, but you can call this way instead

for host, host_output in output.items():
    for line in host_output.stdout:
        pass # consume all the output
    retval = client.get_exit_code(host_output)
   ...

i've had issues with client.join(output) where a problematic host was not responding or hung then it would hang the join call and it wasn't clear who the contributor was.

[pkittenis]

Looks like documentation needs updating - client.join is required for exit codes to work correctly. Or use get_exit_code as above. Would be good to do this automatically on reading output though.

[pkittenis]

As of 1.11.0, client.join is no longer required to get exit code as long as output has been gathered.

Meaning this now works:

for host, host_output in output.items():
    for line in host_output.stdout:
        pass # consume all the output
    # host_output.exit_code is not None
    retval = host_output.exit_code

HostOutput.exit_code is now a dynamic property. ParallelSSHClient.get_exit_codes and get_exit_code are now no-ops and will be removed in 2.0.0.

[gitterspec]

Related issue... Is there a way to get the exit_code without consuming the output (or consuming it silently without flooding the screen)? Even when I use pass, the logger still prints messages. Using client.join(consume_output=True) is similarly not silent and setting it to False does not return an exit_code.