gpg failing on import during test

see: http://lemur.leap.se:8010/builders/linux-runtests/builds/88/steps/Running%20Tests/logs/stdio

src/leap/email/smtp/tests/init.py should be rewritten to use BaseLeapTest.

(from redmine: created on 2013-01-25, closed on 2013-01-29, relates #1508 (closed))