Clear redis cache and precompile assets during update to 6.0. Fix #4874 #4840

As a consequence on the namespaces change from 5.4 to 6.0, after upgrade
lots of links on the dashboard were not working (pointing to projects
without the group part on the url).
Also, after upgrading to 6.0-stable, the network (branch history) function
does not work. The progress bar rotates forever, but the network graph cannot
be generated.

Clearing redis cache fixes those issues.

doc/update/5.4-to-6.0.md

@@ -62,7 +62,7 @@ cd /home/git/gitlab
 # MySQL
 sudo -u git -H bundle install --without development test postgres --deployment
 
-#PostgreSQL
+# PostgreSQL
 sudo -u git -H bundle install --without development test mysql --deployment
 
 sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production
@@ -71,8 +71,12 @@ sudo -u git -H bundle exec rake migrate_global_projects RAILS_ENV=production
 sudo -u git -H bundle exec rake migrate_keys RAILS_ENV=production
 sudo -u git -H bundle exec rake migrate_inline_notes RAILS_ENV=production
 
-sudo -u git -H bundle exec rake assets:precompile RAILS_ENV=production
+# Clear redis cache
+sudo -u git -H bundle exec rake cache:clear RAILS_ENV=production
 
+# Clear and precompile assets
+sudo -u git -H bundle exec rake assets:clean RAILS_ENV=production
+sudo -u git -H bundle exec rake assets:precompile RAILS_ENV=production
 ```
 
 ### 6. Update config files