Fixes #4611,#7353 - control the db_pending_migration/db_pending_seed from installer

This allows tracking the state of migration/seeding in the installer and
making sure the rake tasks are done on subsequential when something goes wrong
the first time.

Also, as part of the `foreman-rake config` calls, we ensure that the settings
are initiated before the httpd starts (preventing the race-conditions
happening when the httpd and rake db:seed start at the same time)
We still need to run something so that the resources that are subscribed to is will be executed.

```puppet
foreman::foreman_config { 'db_pending_migration_true':
  unless_args => '-k db_pending_seed -v false',
} ~>
foreman::rake { 'db:migrate': }
```
We still need to run the `unless`