Turn-off Xvfb auto-display to avoid flaky failures

At times Xvfb is failing because of the inability to start
within 10 seconds.
Set the timeout to 30 seconds and avoid the auto-discover displays
to minimise the probability of future flaky failures.

Change-Id: I1913b4dc437107194b52c39f5b4b7f2704c0577d
diff --git a/jenkins/gerrit-buck-bazel-template.yaml b/jenkins/gerrit-buck-bazel-template.yaml
index 696a982..9ae120e 100644
--- a/jenkins/gerrit-buck-bazel-template.yaml
+++ b/jenkins/gerrit-buck-bazel-template.yaml
@@ -41,11 +41,10 @@
       - timestamps
       - xvfb:
           installation-name: Xvfb
-          auto-display-name: true
+          display-name: 1
           parallel-build: false
-          timeout: 10
+          timeout: 30
           screen: 1024x768x16
-          display-name-offset: 100
           additional-options: -fbdir /tmp
           debug: true
           shutdown-with-build: false
@@ -95,11 +94,10 @@
       - timestamps
       - xvfb:
           installation-name: Xvfb
-          auto-display-name: true
+          display-name: 1
           parallel-build: false
-          timeout: 10
+          timeout: 30
           screen: 1024x768x16
-          display-name-offset: 100
           additional-options: -fbdir /tmp
           debug: true
           shutdown-with-build: false
diff --git a/jenkins/gerrit-verifier.yaml b/jenkins/gerrit-verifier.yaml
index cdc76c5..9dd1bff 100644
--- a/jenkins/gerrit-verifier.yaml
+++ b/jenkins/gerrit-verifier.yaml
@@ -78,11 +78,10 @@
     wrappers:
       - xvfb:
           installation-name: Xvfb
-          auto-display-name: true
+          display-name: 1
           parallel-build: false
-          timeout: 10
+          timeout: 30
           screen: 1024x768x16
-          display-name-offset: 100
           additional-options: -fbdir /tmp
           debug: true
           shutdown-with-build: false