[CI] Fix glance-multistore-cinder-import job

The glance-multistore-cinder-import job is failing with two issues on
unmaintained/yoga.

First, the full job occasionally times out. Increase its timeout to
10800 like on the master branch.

Test tempest.api.image.v2.admin.test_image_caching.ImageCachingTest is
also failing with a timeout: increase image.build_timeout in Tempest
configuration to work around it.

Change-Id: Ib813434538b8af62c16a64663dff626b861d3e81

.zuul.yaml

@@ -247,6 +247,7 @@
 - job:
     name: glance-multistore-cinder-import
     parent: tempest-integrated-storage-import
+    timeout: 10800
     description: |
       The regular import workflow job to test with multiple cinder stores
     vars:
@@ -255,6 +256,11 @@
         GLANCE_ENABLE_MULTIPLE_STORES: True
         CINDER_ENABLED_BACKENDS: lvm:lvmdriver-1,lvm:lvmdriver-2
         GLANCE_CINDER_DEFAULT_BACKEND: lvmdriver-1
+      devstack_local_conf:
+        test-config:
+          "$TEMPEST_CONFIG":
+            image:
+              build_timeout: 600
 
 - job:
     name: tempest-integrated-storage-import-standalone