Fix pdf-docs build failure

With the new release of Sphinx 3.1.0, building blazar pdf docs started
failing with a "! Dimension too large." error.

TeX memory gets exhausted during the pdf build due to the inclusion of
large sample files. With this fix, sample files are included in html but
not in pdf.

Disable other Zuul jobs since some are failing. They will be enabled
again in https://review.opendev.org/#/c/738071/

Change-Id: I1287ebdeab2be521c2d19177560c8467f2acc182
Closes-Bug: #1885250

.zuul.yaml

@@ -36,13 +36,7 @@
       - publish-openstack-docs-pti
       - release-notes-jobs-python3
     check:
-      jobs:
-        - blazar-devstack-dsvm
-        - blazar-devstack-dsvm-ipv6-only
-        - openstack-tox-pylint:
-            voting: false
+      jobs: []
     gate:
       queue: blazar
-      jobs:
-        - blazar-devstack-dsvm
-        - blazar-devstack-dsvm-ipv6-only
+      jobs: []

doc/source/configuration/index.rst

@@ -13,13 +13,18 @@ Reference
    blazar-conf.rst
    nova-conf.rst
 
+.. # NOTE(priteau): Keep sample files for HTML only.
+   # Sample files are too large and cause TeX memory issues.
+   # See bug https://bugs.launchpad.net/blazar/+bug/1885250
 
-Sample Files
-^^^^^^^^^^^^
+.. only:: html
 
-.. toctree::
+   Sample Files
+   ^^^^^^^^^^^^
 
-   samples/blazar-conf.rst
+   .. toctree::
+
+      samples/blazar-conf.rst
 
 Policy
 ------
@@ -31,9 +36,15 @@ Reference
 
    blazar-policy.rst
 
-Sample Files
-^^^^^^^^^^^^
+.. # NOTE(priteau): Keep sample files for HTML only.
+   # Sample files are too large and cause TeX memory issues.
+   # See bug https://bugs.launchpad.net/blazar/+bug/1885250
 
-.. toctree::
+.. only:: html
 
-   samples/blazar-policy.rst
+   Sample Files
+   ^^^^^^^^^^^^
+
+   .. toctree::
+
+      samples/blazar-policy.rst