Avoid db:dev_seed log print when run from its test

The db:dev_seed rake logs info as it progresses as information for the
developer. But that's not needed when ran from its tests file, and it
bloats the travis/rspec output with unnecessary information.

Now the task will always log info unless the rake task receives an
optional argument.

spec/lib/tasks/dev_seed_spec.rb

@@ -5,7 +5,7 @@ Rake.application.rake_require('tasks/db')
 
 describe 'rake db:dev_seed' do
   let :run_rake_task do
-    Rake.application.invoke_task('db:dev_seed')
+    Rake.application.invoke_task('db:dev_seed[avoid_log]')
   end
 
   it 'seeds the database without errors' do