Only initialize the glance_http if service is enabled

This commit just adds a check to see if glance is set as enabled in
the config file before initializing the glance http client. Previously
regardless of whether glance was enabled or not glance_http would
auth against keystone.

Closes-Bug: #1214774
Change-Id: I07127c21d55d58fdb294468a0b74ce2bc54d8719
diff --git a/tempest/services/image/v1/json/image_client.py b/tempest/services/image/v1/json/image_client.py
index 9f5a405..61dd050 100644
--- a/tempest/services/image/v1/json/image_client.py
+++ b/tempest/services/image/v1/json/image_client.py
@@ -36,7 +36,8 @@
         super(ImageClientJSON, self).__init__(config, username, password,
                                               auth_url, tenant_name)
         self.service = self.config.images.catalog_type
-        self.http = self._get_http()
+        if config.service_available.glance:
+            self.http = self._get_http()
 
     def _image_meta_from_headers(self, headers):
         meta = {'properties': {}}
diff --git a/tempest/services/image/v2/json/image_client.py b/tempest/services/image/v2/json/image_client.py
index 3d37267..c654a49 100644
--- a/tempest/services/image/v2/json/image_client.py
+++ b/tempest/services/image/v2/json/image_client.py
@@ -31,7 +31,8 @@
         super(ImageClientV2JSON, self).__init__(config, username, password,
                                                 auth_url, tenant_name)
         self.service = self.config.images.catalog_type
-        self.http = self._get_http()
+        if config.service_available.glance:
+            self.http = self._get_http()
 
     def _get_http(self):
         token, endpoint = self.keystone_auth(self.user, self.password,