Vagrant: slapd must be running, add provision hint to docs

For some reason the initial ldap provisioning might fail even
after ensuring that slapd is running. Yet another `vagrant provision`
will fix the issue.

refs #9453

.puppet/modules/openldap/manifests/init.pp

@@ -28,7 +28,7 @@ class openldap {
       exec { "slapd-schema-${schema}":
         command => "ldapadd -Y EXTERNAL -H ldapi:// -f /etc/openldap/schema/${schema}.ldif",
         group   => 'root',
-        require => Package['openldap-servers'],
+        require => [ Package['openldap-servers'], Service['slapd'] ],
         unless  => "test -n \"$(find /etc/openldap/slapd.d/cn=config/cn=schema/ -name cn={*}${schema}.ldif -print -quit)\"",
         user    => 'root',
       }

doc/vagrant.md

@@ -24,6 +24,8 @@ vagrant up
 > you'll download a plain CentOS base box and Vagrant will automatically
 > provision the environment on the first go.
 
+If the LDAP schema import fails, rerun `vagrant provision`.
+
 After you should be able to browse [localhost:8080/icingaweb2](http://localhost:8080/icingaweb2).
 
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