this will be used to allow the unittests to disable the events
framework. this way, emit() will become a passthrough.

note that, until now, the basetest class is making use of the threaded
version of the client, which launches a zmq tornado-based ioloop. this
is wrong, and will have to be addressed in a future commit. we'll have
to make use of the global EVENTS_ENABLED flag in the txclient version
when those changes are made.

Related: #7259
Relases: 0.4.2

This is needed to get the tests working on environments where zmq was
not initalizated.

The environment variable XDG_CONFIG_HOME is set to get the leap
configuration in the temp folder.

The certificate validity times were converted to local time and later on
compared with UTC time, which caused the certificate not being updated
at the right times.
Add tests to be sure this is not happenning again.
Add a joint pem file for the existing cert and key files to ease test.

- Resolves: #6994

In some systems the used tmp dir is like '/tmp/leap_tests-asdf' and in
others is like '/tmp/username/leap_tests-asdf'.
With this fix we protect the home dir and consider different possible
temp directories.

Using trial there is no setUpClass neither tearDownClass, the setting up
of the environment needs to be in an external class to be able to call
it from inhereted classes.