Add missing whitespace in config description

Change-Id: Ie7e66b9de0a1d14de795166671d31fc9bbeae206
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 0554082..ea9c528 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -427,7 +427,7 @@
 # (string value)
 #alt_password=<None>
 
-# Administrative Username to use forKeystone API requests.
+# Administrative Username to use for Keystone API requests.
 # (string value)
 #admin_username=admin
 
diff --git a/tempest/config.py b/tempest/config.py
index 0fb4491..bbff992 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -78,7 +78,7 @@
                secret=True),
     cfg.StrOpt('admin_username',
                default='admin',
-               help="Administrative Username to use for"
+               help="Administrative Username to use for "
                     "Keystone API requests."),
     cfg.StrOpt('admin_tenant_name',
                default='admin',