ignoring the result fixes a scan-build error.  besides, ignore() should be
more appropriate choice for what it intends to do anyway.

Or more specifically, make the tests not depend on dict ordering

reviewed on jabber (muks)

http://git.bind10.isc.org/~tester/builder//BIND10-cppcheck/20130125000502-FreeBSD8-amd64-GCC/logs/unittests.out

Due to the difference of timing of invoking datetime.now(), _stop_timer()
should return greater than one second. But depending on runtime environment, it
happens to return one second exactly. For supporting this behaviour, regarding
checking of the returned value, 'assertGreater' is changed to
'assertGreaterEqual'.

indent on description
use a tab before the keyword type.
use two tabs before the committer username.
line too long

the latter is relatively new and doesn't work for all of our supported
python versions.  will fix a buildbot report.  committing at my discretion.

the original version didn't have a problem because the constructor
should never be used in python wrappers, but I do this to silence cppcheck.
the change is small anyway.

as this seemed to be a controversial move.

- small updates to doc and comments
- changed __try_login to _try_login
- replaced direct calls to print() with self._print(), to override in tests
  (and more easily check output)
- added some more test cases
- made cmdctl tests fail is environment vars aren't set