Environment variable DISTRIBUTION_SUFFIX is not set

[andsel]

We have to check before that AppSearch comes also in oss distribution.
However the problem seen in Travis logs is that despite the assignment done in https://github.com/logstash-plugins/.ci/blob/2ab436bc3ce69bcfc01d32a8fe279f8839e34325/docker-setup.sh#L33-L37 the variable seems without value: https://travis-ci.org/github/logstash-plugins/logstash-output-elastic_app_search/jobs/706134786#L227 while the same has value in Elasticsearch output plugin: https://travis-ci.org/github/logstash-plugins/logstash-output-elasticsearch/jobs/704794610#L222

[andsel]

Perhaps this is the cause of some flaky tests in Travis for OSS and Logstash branch 7.x where we get:

appsearch_1_13a473777159 | ERROR: org.jruby.exceptions.SystemExit: (SystemExit) exit
appsearch_1_13a473777159 | org.jruby.exceptions.SystemExit: (SystemExit) exit
appsearch_1_13a473777159 | 	at org.jruby.RubyKernel.exit(org/jruby/RubyKernel.java:751)
appsearch_1_13a473777159 | 	at org.jruby.RubyKernel.exit(org/jruby/RubyKernel.java:714)
appsearch_1_13a473777159 | 	at RUBY.fatal_error(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/shared_togo/lib/shared_togo.class:1067)
appsearch_1_13a473777159 | 	at RUBY.check_elasticsearch_license!(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/shared_togo/lib/shared_togo.class:252)
appsearch_1_13a473777159 | 	at RUBY.configure!(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/shared_togo/lib/shared_togo.class:246)
appsearch_1_13a473777159 | 	at RUBY.<main>(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/config/application.class:20)
appsearch_1_13a473777159 | 	at org.jruby.RubyKernel.load(org/jruby/RubyKernel.java:1013)
appsearch_1_13a473777159 | 	at RUBY.<main>(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/config/application.rb:1)
appsearch_1_13a473777159 | 	at org.jruby.RubyKernel.require(org/jruby/RubyKernel.java:978)
appsearch_1_13a473777159 | 	at RUBY.<main>(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/gems/gems/railties-4.2.11.1/lib/rails/commands/runner.rb:51)
appsearch_1_13a473777159 | 	at org.jruby.RubyKernel.require(org/jruby/RubyKernel.java:978)
appsearch_1_13a473777159 | 	at RUBY.require_command!(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/gems/gems/railties-4.2.11.1/lib/rails/commands/commands_tasks.rb:123)
appsearch_1_13a473777159 | 	at RUBY.runner(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/gems/gems/railties-4.2.11.1/lib/rails/commands/commands_tasks.rb:90)
appsearch_1_13a473777159 | 	at RUBY.run_command!(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/gems/gems/railties-4.2.11.1/lib/rails/commands/commands_tasks.rb:39)
appsearch_1_13a473777159 | 	at RUBY.<main>(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/gems/gems/railties-4.2.11.1/lib/rails/commands.rb:17)
appsearch_1_13a473777159 | 	at org.jruby.RubyKernel.require(org/jruby/RubyKernel.java:978)
appsearch_1_13a473777159 | 	at usr.share.enterprise_minus_search.tmp.jruby5285554826713037240extract.$_dot_.META_minus_INF.rails.<main>(/usr/share/enterprise-search/tmp/jruby5285554826713037240extract/./META-INF/rails.rb:7)