Fixed many subnet related test cases.

Assertion for `test_create_subnet_3` depends on whether checkbox
or selection list exists.

Fixed many other miscellaneous test cases.
Fixed the UI role tests.

Updated the data for role tests accordingly, earlier data was not
right as per the test.

Also using 255 chars would not be needed, if required we can have
a separate test with a separate locator to simplify things.

The issue is the locator itself needs to be tweaked between it's
usage with locale and long char length tests.
Merge pull request #1795 from kbidarkar/fix-subnet-tests

Fixed many subnet related test cases.
Merge pull request #1794 from kbidarkar/fix-role-tests

Fixed the UI role tests.
Do not try to update a repository's content_type

From IRC:

    <ichimonji10> Hey all. Is it possible to update the content_type of a
    repository?
    <jsherrill> ichimonji10: its not
    <jsherrill> you have to delete and re-create

This fixes a failing Jenkins test. Updated test output:

    $ nosetests tests/foreman/api/test_repository.py -m test_update
    ....S........
    ----------------------------------------------------------------------
    Ran 13 tests in 29.033s

    OK (SKIP=1)
Merge pull request #1797 from Ichimonji10/repo-update

Do not try to update a repository's content_type