event_hub_connection string can be a environment variable

[ryanmac8]

When using the advance configuration, exception errors are thrown when using environment variables for the event_hub_connection string.

[ERROR] 2019-05-06 13:38:34.818 [Ruby-0-Thread-11: /usr/share/logstash/vendor/bundle/jruby/2.3.0/gems/logstash-input-azure_event_hubs-1.0.4/lib/logstash/inputs/azure_event_hubs.rb:381] azureeventhubs - Event Hub failed during initialization. {:event_hub_name=>"********", :exception=>com.microsoft.azure.eventhubs.IllegalConnectionStringFormatException: Connection String cannot be parsed., :backtrace=>["com.microsoft.azure.eventhubs.ConnectionStringBuilder.parseConnectionString(com/microsoft/azure/eventhubs/ConnectionStringBuilder.java:314)", "com.microsoft.azure.eventhubs.ConnectionStringBuilder.<init>(com/microsoft/azure/eventhubs/ConnectionStringBuilder.java:100)", "com.microsoft.azure.eventprocessorhost.EventProcessorHost.<init>(com/microsoft/azure/eventprocessorhost/EventProcessorHost.java:245)", "com.microsoft.azure.eventprocessorhost.EventProcessorHost.<init>(com/microsoft/azure/eventprocessorhost/EventProcessorHost.java:173)", "com.microsoft.azure.eventprocessorhost.EventProcessorHost.<init>(com/microsoft/azure/eventprocessorhost/EventProcessorHost.java:157)", "com.microsoft.azure.eventprocessorhost.EventProcessorHost.<init>(com/microsoft/azure/eventprocessorhost/EventProcessorHost.java:101)", "java.lang.reflect.Constructor.newInstance(java/lang/reflect/Constructor.java:423)", "org.jruby.javasupport.JavaConstructor.newInstanceDirect(org/jruby/javasupport/JavaConstructor.java:246)", "org.jruby.RubyClass.newInstance(org/jruby/RubyClass.java:1022)", "org.jruby.RubyClass$INVOKER$i$newInstance.call(org/jruby/RubyClass$INVOKER$i$newInstance.gen)", "RUBY.block in run(/usr/share/logstash/vendor/bundle/jruby/2.3.0/gems/logstash-input-azure_event_hubs-1.0.4/lib/logstash/inputs/azure_event_hubs.rb:386)", "org.jruby.RubyProc.call(org/jruby/RubyProc.java:289)", "org.jruby.RubyProc.call(org/jruby/RubyProc.java:246)", "java.lang.Thread.run(java/lang/Thread.java:748)"]}

[lukasmrtvy]

I have same problem...