Fix db:migrate for fresh installs

lib/tasks/migrate/schema_check.rake

 desc 'Configures the database by running migrate, or by loading the schema and seeding if needed'
 task schema_version_check: :environment do
-  if ActiveRecord::Migrator.current_version < Gitlab::Database::MIN_SCHEMA_VERSION
+  schema_version = ActiveRecord::Migrator.current_version
+
+  # Ensure migrations are being run from a supported schema version
+  # A schema verison of 0 is a fresh db, and should be safe to run migrations
+  # But a database with existing migrations less than our min version is not
+  if schema_version > 0 && schema_version < Gitlab::Database::MIN_SCHEMA_VERSION
     raise "Your current database version is too old to be migrated. " \
           "You should upgrade to GitLab #{Gitlab::Database::MIN_SCHEMA_GITLAB_VERSION} before moving to this version. " \
           "Please see https://docs.gitlab.com/ee/policy/maintenance.html#upgrade-recommendations"