migration: Create migrate_tls_hostname() function

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

---

Moved the type to const char * (vladimir)
diff --git a/migration/options.c b/migration/options.c
index 014aecc..1aa9575 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -596,6 +596,13 @@
     return s->parameters.tls_creds;
 }
 
+const char *migrate_tls_hostname(void)
+{
+    MigrationState *s = migrate_get_current();
+
+    return s->parameters.tls_hostname;
+}
+
 uint64_t migrate_xbzrle_cache_size(void)
 {
     MigrationState *s = migrate_get_current();