Rename a poorly named field of a test class
Add logging assertion to GitAPITestCase

Preparing to add timeout to CheckoutCommand.  Needed a way to assert
that the timeout value was used, without waiting for timeout to
expire.
Check timeout is reported in GitAPITestCase based tests

Also provides an assertion prevention technique because some of the
tests need to be excluded from the check.  Excluded tests are those
which perform no operation which would involve a timeout.
Define and use TIMEOUT_LOG_PREFIX in log for timeout tests
Extend LogHandler test class to extract timeout values

Also added a test of LogHandler class.
Assert that all timeouts in API tests are default value
Use symbolic reference instead of hard coded string
Test timeout in fetch()
Only construct timeout expectations array if timeout is visible
Set timeout on clone_()
Add timeout test for submodule update
Implement timeout on checkout as progress towards [FIX JENKINS-22400]

Does not complete the fix of JENKINS-22400 because the git plugin
needs to call the newly added timeout() method.

Does not complete the [FIX JENKINS-20387] because it has not yet added
timeout to clean.