Fix bad variable ref

Author: Juuso Mäyränen

spec/inputs/redis_spec.rb

@@ -73,7 +73,7 @@ def process(conf, event_count)
       input {
         redis {
           type => "blah"
-          key => "#{key}.*"
+          key => "#{key_base}.*"
           data_type => "pattern_list"
           batch_count => 1
         }
@@ -94,7 +94,7 @@ def process(conf, event_count)
       input {
         redis {
           type => "blah"
-          key => "#{key}.*"
+          key => "#{key_base}.*"
           data_type => "pattern_list"
           batch_count => 125
         }