Ensure publicdocs.sh will fail on included scripts failure

An unexpected behaviour has been spotted, when build-all-rst.sh
failure was still resulting in publishdocs.sh successfull execution.

As a result, .root-marker was not produced, so while promote job
was successfull, it was not actually changing any content on AFS.

Moreover, produced artifact was not containing all intended content,
and was missing some guides, while it was treated as a successfull run[1],
with logs stating the following:

```
2025-06-29 23:15:43.683195 | ubuntu-jammy | build finished with problems, 1 warning (with warnings treated as errors).
2025-06-29 23:16:44.988836 | ubuntu-jammy |   publishdocs: OK (66.94=setup[0.03]+cmd[64.81,2.10,0.00] seconds)
2025-06-29 23:16:44.988844 | ubuntu-jammy |   congratulations :) (66.98 seconds)
2025-06-29 23:16:45.335764 | ubuntu-jammy | ok: Runtime: 0:01:07.091357
```

While original issue was fixed in [2], we add `set` to both scripts
to ensure that such false-positive behaviour would not occur in the future.

[1] https://zuul.opendev.org/t/openstack/build/37a9b4537fc9495c99974bf011d09f00
[2] https://review.opendev.org/c/openstack/openstack-manuals/+/951429
Change-Id: I60654d07d3b8e731274c82351253463c10ea5f2b
Signed-off-by: Dmitriy Rabotyagov <dmitriy.rabotyagov@cleura.com>

tools/build-all-rst.sh

@@ -1,4 +1,5 @@
 #!/bin/bash -e
+set -e -u -x
 
 mkdir -p publish-docs/html
 

tools/publishdocs.sh

@@ -12,6 +12,9 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+## Shell Opts
+set -e -u -x
+
 mkdir -p publish-docs/html
 
 # Build all RST guides including PDF files