OF-477 correct tooltip message in setup

src/i18n/openfire_i18n_en.properties

@@ -2123,7 +2123,7 @@ setup.host.settings.domain=XMPP Domain Name:
 setup.host.settings.domain.help=The name of the XMPP domain that this server will be part of (for example: example.org). If this server will be part of an Openfire cluster, each server must have the same XMPP domain name.
 setup.host.settings.invalid_domain=Invalid domain.
 setup.host.settings.fqdn=Server Host Name (FQDN):
-setup.host.settings.fqdn.help=The fully qualified domain name of this server (for example: openfire.example.org). If this server will be part of an Openfire cluster, each server must have the same host name.
+setup.host.settings.fqdn.help=The fully qualified domain name of this server (for example: openfire.example.org). If this server will be part of an Openfire cluster, each server must have an unique server host name.
 setup.host.settings.invalid_fqdn=Invalid host name.
 setup.host.settings.port=Admin Console Port:
 setup.host.settings.secure_port=Secure Admin Console Port: