Use localhost for test database connections

This fixes an issue if using psql container in docker and running the tests on the host machine. By specifying "localhost" this ensures the connection is done via TCP rather than sockets, which is needed to connect to the container.

Follows govuk-forms/forms-runner#1588

Author: chao-xian

config/database.yml

@@ -58,6 +58,9 @@ development:
 test:
   <<: *default
   database: forms_admin_test
+  username: postgres
+  password: postgres
+  host: localhost
   gssencmode: disable # needed to stop spring from segfaulting
 
 # As with config/credentials.yml, you never want to store sensitive information,