Add a "set -e" to the dind-sidecar test script and run the image once.

I was bitten by this test not having one, when the "docker build"
failed but we continued on executing anyway. I did a cursory look
at the other tests, and they either already have this or are so
short/simple that it doesn't matter.

Ref tektoncd#3628

examples/v1alpha1/taskruns/dind-sidecar.yaml

@@ -19,6 +19,7 @@ spec:
         value: /certs/client
       script: |
           #!/usr/bin/env sh
+          set -e
           # Run a Docker container.
           docker run busybox echo hello
 
@@ -28,7 +29,7 @@ spec:
           RUN apt-get update
           ENTRYPOINT ["echo", "hello"]
           EOF
-          docker build -t hello . && docker run hello
+          docker build -t hello .
           docker images
 
           # ...then run it!

examples/v1beta1/taskruns/dind-sidecar.yaml

@@ -19,6 +19,7 @@ spec:
         value: /certs/client
       script: |
           #!/usr/bin/env sh
+          set -e
           # Run a Docker container.
           docker run busybox echo hello
 
@@ -28,7 +29,7 @@ spec:
           RUN apt-get update
           ENTRYPOINT ["echo", "hello"]
           EOF
-          docker build -t hello . && docker run hello
+          docker build -t hello .
           docker images
 
           # ...then run it!