Shard 600_proxy_docker_py into 4.

[tomwilkie]

Fixes #1239

[tomwilkie]

Oh Yeah:

Test ./601_proxy_docker_py_test.sh needs 1 hosts
Test ./602_proxy_docker_py_test.sh needs 1 hosts
Test ./603_proxy_docker_py_test.sh needs 1 hosts
Test ./604_proxy_docker_py_test.sh needs 1 hosts
>>> Running ./604_proxy_docker_py_test.sh on [host1.us-central1-a.positive-cocoa-90213]
>>> Running ./603_proxy_docker_py_test.sh on [host2.us-central1-a.positive-cocoa-90213]
>>> Running ./602_proxy_docker_py_test.sh on [host3.us-central1-a.positive-cocoa-90213]
>>> Running ./601_proxy_docker_py_test.sh on [host4.us-central1-a.positive-cocoa-90213]
>>> Test ./604_proxy_docker_py_test.sh finished with success after 36.4 secs
Run docker-py test suite against the proxy
a5d35557a87b110e912461e4039f765721b35d509248ff56a1800a3a93ca6a23
...............
----------------------------------------------------------------------
Ran 15 tests in 19.075s

OK
all 1 tests passed in 35.476s.

>>> Test ./601_proxy_docker_py_test.sh finished with success after 51.7 secs
Run docker-py test suite against the proxy
e461c0a28d58e9d616b95280268c373de856a3fce16ff47f0001cc2ee202f6ab
...........
----------------------------------------------------------------------
Ran 11 tests in 10.763s

OK
all 1 tests passed in 50.750s.

>>> Test ./602_proxy_docker_py_test.sh finished with success after 59.2 secs
Run docker-py test suite against the proxy
bf498f26cd70cee43f6f6bebe03ec96b0d50b44d6763649024af359b9143dcd6
..s.............
----------------------------------------------------------------------
Ran 16 tests in 16.870s

OK (skipped=1)
all 1 tests passed in 58.132s.

>>> Test ./603_proxy_docker_py_test.sh finished with success after 70.2 secs
Run docker-py test suite against the proxy
fcb1bfee7450df4998d68be8a526f547fe21d96b0de1a9d86c95f0b88fef7e70
...................
----------------------------------------------------------------------
Ran 19 tests in 26.679s

OK
all 1 tests passed in 69.227s.

>>> Ran 4 tests, all succeeded