Add title to 'add' dialog for 'Host' entity

To improve translation quality the title of 'Add' dialog should be
specified explicitly in the spec and should be an entire sentence.

Fixes: https://pagure.io/freeipa/issue/7707
Reviewed-By: Serhii Tsymbaliuk <stsymbal@redhat.com>

install/ui/src/freeipa/host.js

@@ -444,6 +444,7 @@ return {
     ],
     standard_association_facets: true,
     adder_dialog: {
+        title: '@i18n:objects.host.add',
         $factory: IPA.host_adder_dialog,
         height: 300,
         sections: [

ipaserver/plugins/internal.py

@@ -796,6 +796,7 @@ class i18n_messages(Command):
                 "unmatched": _("Unmatched"),
             },
             "host": {
+                "add": _("Add host"),
                 "certificate": _("Host Certificate"),
                 "cn": _("Host Name"),
                 "delete_key_unprovision": _("Delete Key, Unprovision"),