Fix execution times in lxd 3.0.1 and add pipelining support to execute

[lasizoillo]

Fix issue #316 and issue #244

It works (tox and integration tests) with lxd versions 3.0.1 and 2.0.11

Can be tested with this script to view some new features:

from pylxd import Client
import io
import logging

logger = logging.getLogger(__name__)
handler = logging.StreamHandler()
handler.setFormatter(
    logging.Formatter("%(relativeCreated)6d %(threadName)s %(message)s")
)
logger.addHandler(handler)
logger.setLevel(logging.INFO)

c = Client()
cont = c.containers.all()[0]
if cont.status != "Running":
    cont.start(wait=True)

# Stdin demo
logger.info(cont.execute(["cat", "-"], stdin_payload=open(__file__)).stdout)
logger.info(cont.execute(["cat", "-"], stdin_payload="hola"))
logger.info(cont.execute(["cat", "-"], stdin_payload=b"hola"))
logger.info(cont.execute(["cat", "-"], stdin_payload=io.StringIO("hola")))
logger.info(cont.execute(["cat", "-"], stdin_payload=io.BytesIO(b"hola")))


# Stdout demo
def handle_out(msg):
    logger.info(msg)


cont.execute(
    [
        "bash", "-c",
        'while read  c; do echo "$c"; sleep 1; done < /etc/hosts'
    ], stdout_handler=handle_out
)

container.execute is retro-compatible but adds pipeline features. Now you can communicate with your commands via stdin and manage output while command is executing.

[codecov-io]

Codecov Report

Merging #321 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #321      +/-   ##
==========================================
- Coverage   96.84%   96.84%   -0.01%     
==========================================
  Files          11       11              
  Lines         920      918       -2     
  Branches      106      106              
==========================================
- Hits          891      889       -2     
  Misses         10       10              
  Partials       19       19

Impacted Files	Coverage Δ
pylxd/models/container.py	91.06% <100%> (-0.08%)	⬇️

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[ajkavanagh]

Thanks for putting this together. However, there seems to be something very odd going on with the PR as it includes a bunch of already committed patches? Perhaps you need a git fetch/merge and/or rebase from this master to only submit the PR that is relevant to this change?

I'll do some testing with the branch/commit from your repo as well. Thanks very much.
(Sorry for the delay; I've been on holiday and away).

[ajkavanagh]

Needs rebasing (I think) as it has many already committed changes in the PR.

[lasizoillo]

Rebased

[Silentphantom62]

@ajkavanagh Can you please review this? Have been waiting on a fix for this for a while.

[ajkavanagh]

@Silentphantom62 and @lasizoillo -- sorry for the delay; just got back from holiday -- I'll review & do some integration tests today.

[ajkavanagh]

Okay, I've tested this in 1604 and 1804 hosts and containers, and everything seems to work great. Thanks very much for the PR, and sorry for the delay in getting it merged.

[Silentphantom62]

Thanks @ajkavanagh what's the tentative release date of this fix?