Bump alpine and nginx to latest stable version & Fix deps for build amplify

[ghost]

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[ghost]

Added commits that fix the problem with starting nginx-amplify-agent.py and debugging the cause.

/ # ./entrypoint.sh
starting nginx ...
updating /etc/amplify-agent/agent.conf ...
 ---> using api_key = secret
 ---> using imagename = dev
starting amplify-agent ...
couldn't start the agent, please check /var/log/amplify-agent/agent.log

But /var/log/amplify-agent/agent.log is empty. All output was sent to /dev/null.

/ # grep "starting amplify-agent" -A1 entrypoint.sh
echo "starting amplify-agent ..."
nginx-amplify-agent.py start --config=/etc/amplify-agent/agent.conf > /dev/null 2>&1 < /dev/null

Starting without output redirection

/ # nginx-amplify-agent.py start --config=/etc/amplify-agent/agent.conf

Something failed:

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/nginx_amplify_agent-1.1.0-py2.7.egg/amplify/agent/common/util/configreader.py", line 71, in test
    skip_uuid=True
  File "/usr/lib/python2.7/site-packages/nginx_amplify_agent-1.1.0-py2.7.egg/amplify/agent/common/context.py", line 94, in setup
    self._setup_http_client()
  File "/usr/lib/python2.7/site-packages/nginx_amplify_agent-1.1.0-py2.7.egg/amplify/agent/common/context.py", line 218, in _setup_http_client
    from amplify.agent.common.util.http import HTTPClient
  File "/usr/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__
    result = _import(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/nginx_amplify_agent-1.1.0-py2.7.egg/amplify/agent/common/util/http.py", line 4, in <module>
    import ujson
  File "/usr/lib/python2.7/site-packages/gevent/builtins.py", line 93, in __import__
    result = _import(*args, **kwargs)
ImportError: Error relocating /usr/lib/python2.7/site-packages/ujson.so: Buffer_AppendShortHexUnchecked: symbol not found

Cause of error ultrajson/ultrajson#326