Fix failed tests for "rake test:integration"

[junaruga]

I fixed below failed tests for "rake test:integration".

$ bundle exec rake test:integration
cd test/shell; sh run.sh
t1 FAIL
t2 FAIL
t3 FAIL
rake aborted!
Command failed with status (3): [cd test/shell; sh run.sh...]
/home/jaruga/git/puma/Rakefile:160:in `block (2 levels) in <top (required)>'
/home/jaruga/git/puma/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/exe/rake:27:in `<top (required)>'
/usr/local/ruby-2.4.1/bin/bundle:22:in `load'
/usr/local/ruby-2.4.1/bin/bundle:22:in `<main>'
Tasks: TOP => test:integration
(See full trace by running task with --trace)

It works after this modification.

$ bundle exec rake test:integration
cd test/shell; sh run.sh
t1 OK
t2 OK
t3 OK

But why is this "test:integration" test not included in Travis and Appveyor CI test?