Update `sync_time` configuration after change in GitLab
Related to https://gitlab.com/gitlab-org/gitlab-ee/issues/364
Depending on the outcome of the above issue, Omnibus config will need to be updated. Namely, if sync_time
becomes a 'global' LDAP configuration we will need to adjust the template to use the gitlab_rails['ldap_sync_time']
value again instead of the provider-specific one.