Fix API version comparison for 1.10

[dangra]

v1.10 is current latest: http://docs.docker.io/en/latest/reference/api/docker_remote_api/#v1-10

docker-py fails to compare it due to a float based implementation:

>>> from docker import utils
>>> utils.compare_version('1.8', '1.9')
0.09999999999999987
>>> utils.compare_version('1.9', '1.10')
-0.7999999999999998

after this change:

>>> utils.compare_version('1.8', '1.9')
1
>>> utils.compare_version('1.9', '1.10')
1

[mpetazzoni]

Thanks. cmp() doesn't exist in Python 3 though, as shown by the build failing. Could you fix this in your change? Thanks!

[dangra]

@mpetazzoni : thanks for pointing it. should be fixed now.

[dangra]

is trunk broken at the moment? some tests failing with unrelated error:

AssertionError: Command should not raise exception: local variable 'authcfg' referenced before assignment

[shin-]

Odd. master seems to be passing though.

[dangra]

the new compare_version was returning the result inverted and that triggered two hidden bugs in support code for older API versions.

I rebased and included a fix for those errors too, but as the codepath for old API versions is not tested it is hard to tell when it will break again, how long do you plan to support old API versions in docker-py?