Add workaround for slow openssl loading (LOGSTASH-1223)

Loading `openssl` within the flatjar is super slow. For some reason it is fast with an empty `$LOAD_PATH`. No idea what's going on, yet.

I ran into this while testing the 1.2 release. It's not pretty but removes a 45 second delay while starting logstash on my i7 notebook.

I ran the `jar` and `flatjar` testsuites, they are fine.

(I would update LOGSTASH-1223 but I cannot create a JIRA account at the moment - captcha broken...)