proxy configuration and ssl configuration

[karthikr77]

Referring to https://discuss.elastic.co/t/redis-input-plugin-proxy-and-ssl/111195

Was testing Azure Redis with logstash and beats, which comes by default only with SSL enabled, and have to disable SSL explicitly. Moreover, to access redis, there is proxy to pass in some scenarios.

W.r.t beats, there are settings to config proxy and ssl - but, logstash there is none. Had to turn off SSL and take the logstash outside proxy to get working. Though Azure Redis, the situation is common for certain redis implementations.

Shall we add similar settings for logstash to cover proxy and ssl. If it is already present/I'm missing something, please reply to the thread in elastic.