MINOR: upgrade pip from 20.2.2 to 21.1.1 (apache#10661)

The following error happens on my mac m1 when building docker image for system tests.

Collecting pynacl
  Using cached PyNaCl-1.4.0.tar.gz (3.4 MB)
  Installing build dependencies ... error
  ERROR: Command errored out with exit status 1:
   command: /usr/bin/python3 /usr/local/lib/python3.8/dist-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-k867aac0/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- 'setuptools>=40.8.0' wheel 'cffi>=1.4.1; python_implementation != '"'"'PyPy'"'"''
       cwd: None
  Complete output (14 lines):
  Traceback (most recent call last):
    File "/usr/lib/python3.8/runpy.py", line 194, in _run_module_as_main
      return _run_code(code, main_globals, None,
    File "/usr/lib/python3.8/runpy.py", line 87, in _run_code
      exec(code, run_globals)
    File "/usr/local/lib/python3.8/dist-packages/pip/__main__.py", line 23, in <module>
      from pip._internal.cli.main import main as _main  # isort:skip # noqa
    File "/usr/local/lib/python3.8/dist-packages/pip/_internal/cli/main.py", line 5, in <module>
      import locale
    File "/usr/lib/python3.8/locale.py", line 16, in <module>
      import re
    File "/usr/lib/python3.8/re.py", line 145, in <module>
      class RegexFlag(enum.IntFlag):
  AttributeError: module 'enum' has no attribute 'IntFlag'
  ----------------------------------------
ERROR: Command errored out with exit status 1: /usr/bin/python3 /usr/local/lib/python3.8/dist-packages/pip install --ignore-installed --no-user --prefix /tmp/pip-build-env-k867aac0/overlay --no-warn-script-location --no-binary :none: --only-binary :none: -i https://pypi.org/simple -- 'setuptools>=40.8.0' wheel 'cffi>=1.4.1; python_implementation != '"'"'PyPy'"'"'' Check the logs for full command output.

There was a related issue: pypa/pip#9689 and it is already fixed by pypa/pip#9689 (included by pip 21.1.1). I test the pip 21.1.1 and it works well on mac m1.

Reviewers: Ismael Juma <[email protected]>

tests/docker/Dockerfile

@@ -34,7 +34,7 @@ LABEL ducker.creator=$ducker_creator
 # Update Linux and install necessary utilities.
 # we have to install git since it is included in openjdk:8 but not openjdk:11
 RUN apt update && apt install -y sudo git netcat iptables rsync unzip wget curl jq coreutils openssh-server net-tools vim python3-pip python3-dev libffi-dev libssl-dev cmake pkg-config libfuse-dev iperf traceroute && apt-get -y clean
-RUN python3 -m pip install -U pip==20.2.2;
+RUN python3 -m pip install -U pip==21.1.1;
 RUN pip3 install --upgrade cffi virtualenv pyasn1 boto3 pycrypto pywinrm ipaddress enum34 && pip3 install --upgrade ducktape==0.8.1
 
 # Set up ssh