IdP metadata parser: fix singleSignOnService processing

[jgehrcke]

There is a typo in the new idp_metadata_parser module: it consumes the singleLogoutService XML tag for populating idp_sso_url, instead of the singleSignOnService tag. This PR fixes the typo and adjusts the tests.

Parser tests pass:

$ python setup.py test --test-suite tests.src.OneLogin.saml2_tests.idp_metadata_parser_test
running test
Searching for xmlsec>=0.6.0
Best match: xmlsec 0.6.0
Processing xmlsec-0.6.0-py3.4-linux-x86_64.egg

Using /home/jp/dev/python3-saml/.eggs/xmlsec-0.6.0-py3.4-linux-x86_64.egg
Searching for isodate>=0.5.0
Best match: isodate 0.5.4
Processing isodate-0.5.4-py3.4.egg

Using /home/jp/dev/python3-saml/.eggs/isodate-0.5.4-py3.4.egg
running egg_info
writing dependency_links to src/python3_saml.egg-info/dependency_links.txt
writing src/python3_saml.egg-info/PKG-INFO
writing top-level names to src/python3_saml.egg-info/top_level.txt
writing requirements to src/python3_saml.egg-info/requires.txt
reading manifest file 'src/python3_saml.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
warning: no previously-included files matching '__pycache__' found under directory '*'
warning: no previously-included files matching '*.py[co]' found under directory '*'
writing manifest file 'src/python3_saml.egg-info/SOURCES.txt'
running build_ext
testGetMetadata (tests.src.OneLogin.saml2_tests.idp_metadata_parser_test.OneLogin_Saml2_IdPMetadataParser_Test) ... ok
testMergeSettings (tests.src.OneLogin.saml2_tests.idp_metadata_parser_test.OneLogin_Saml2_IdPMetadataParser_Test) ... ok
testParse (tests.src.OneLogin.saml2_tests.idp_metadata_parser_test.OneLogin_Saml2_IdPMetadataParser_Test) ... ok
testParseRemote (tests.src.OneLogin.saml2_tests.idp_metadata_parser_test.OneLogin_Saml2_IdPMetadataParser_Test) ... ok

----------------------------------------------------------------------
Ran 4 tests in 2.137s

OK

Note that the test data also specifies SingleLogoutServices:

$ curl https://www.testshib.org/metadata/testshib-providers.xml | grep -i singlelogout
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 20563  100 20563    0     0  17912      0  0:00:01  0:00:01 --:--:-- 17927
            <SingleLogoutService Location="https://sp.testshib.org/Shibboleth.sso/SLO/SOAP"
            <SingleLogoutService Location="https://sp.testshib.org/Shibboleth.sso/SLO/Redirect"
            <SingleLogoutService Location="https://sp.testshib.org/Shibboleth.sso/SLO/POST"
            <SingleLogoutService Location="https://sp.testshib.org/Shibboleth.sso/SLO/Artifact"

They are part of the SPSSODescriptor tag which is not looked into by the IdP parser. So, the expected_data in the tests does not contain any SLSs.

That's the data the IdP parser currently (with the change from this PR) creates when parsing https://www.testshib.org/metadata/testshib-providers.xml:

{
    "sp": {
        "NameIDFormat": "urn:mace:shibboleth:1.0:nameIdentifier"
    },
    "idp": {
        "singleSignOnService": {
            "url": "https://idp.testshib.org/idp/profile/SAML2/Redirect/SSO"
        },
        "entityId": "https://idp.testshib.org/idp/shibboleth"
    }
}

@pitbulk I hope this is now as expected. Please review, thanks!