Fix unicorn crash
Fix unicorn crash

Unicorn verison 5.5.0 broke unicorn_rails. Ensure we don't install that version
https://bogomips.org/unicorn-public/20190307022859.mxz7m3mbspujo4c2@dcvr/

Fixes: #392

Signed-off-by: Cormier, Jonathan <94278db6987355808b2e44bbe88db00b9ea77e5a@criticallink.com>

sameersbn/docker-redmine,sameersbn/docker-redmine,otsuka512/docker-redmine,otsuka512/docker-redmine,otsuka512/docker-redmine,sameersbn/docker-redmine