Replace all Ubuntu 16.04 with Ubuntu18.04 image

Change-Id: I86b84957145f7c1f253d3158e42e015c322788eb
diff --git a/jjb/voltha-e2e.yaml b/jjb/voltha-e2e.yaml
index e9d335d..6b89909 100755
--- a/jjb/voltha-e2e.yaml
+++ b/jjb/voltha-e2e.yaml
@@ -72,7 +72,7 @@
       - 'voltha-periodic-test':
           name: 'periodic-voltha-openonu-go-test-bbsim'
           pipeline-script: 'voltha-openonu-go-test-bbsim.groovy'
-          build-node: 'ubuntu16.04-basebuild-8c-15g'
+          build-node: 'ubuntu18.04-basebuild-8c-15g'
           make-target: openonu-go-adapter-test
           make-target-1t4gemtest: 1t4gem-openonu-go-adapter-test
           make-target-1t8gemtest: 1t8gem-openonu-go-adapter-test
@@ -86,7 +86,7 @@
       - 'voltha-periodic-test':
           name: 'periodic-voltha-openonu-go-test-bbsim-2.7'
           pipeline-script: 'voltha-openonu-go-test-bbsim.groovy'
-          build-node: 'ubuntu16.04-basebuild-8c-15g'
+          build-node: 'ubuntu18.04-basebuild-8c-15g'
           make-target: openonu-go-adapter-test
           make-target-1t4gemtest: 1t4gem-openonu-go-adapter-test
           make-target-1t8gemtest: 1t8gem-openonu-go-adapter-test
@@ -100,7 +100,7 @@
       - 'voltha-periodic-test':
           name: 'periodic-voltha-multiple-olts-openonu-go-test-bbsim'
           pipeline-script: 'voltha-openonu-go-test-bbsim.groovy'
-          build-node: 'ubuntu16.04-basebuild-8c-15g'
+          build-node: 'ubuntu18.04-basebuild-8c-15g'
           make-target: openonu-go-adapter-multi-olt-test
           make-target-1t4gemtest: 1t4gem-openonu-go-adapter-multi-olt-test
           make-target-1t8gemtest: 1t8gem-openonu-go-adapter-multi-olt-test
@@ -117,7 +117,7 @@
       - 'voltha-periodic-test':
           name: 'periodic-voltha-multiple-olts-openonu-go-test-bbsim-2.7'
           pipeline-script: 'voltha-openonu-go-test-bbsim.groovy'
-          build-node: 'ubuntu16.04-basebuild-8c-15g'
+          build-node: 'ubuntu18.04-basebuild-8c-15g'
           make-target: openonu-go-adapter-multi-olt-test
           make-target-1t4gemtest: 1t4gem-openonu-go-adapter-multi-olt-test
           make-target-1t8gemtest: 1t8gem-openonu-go-adapter-multi-olt-test
@@ -166,7 +166,7 @@
       - 'voltha-periodic-test':
           name: 'periodic-voltha-etcd-test'
           pipeline-script: 'voltha-system-test-bbsim.groovy'
-          build-node: 'ubuntu16.04-basebuild-4c-8g'
+          build-node: 'ubuntu18.04-basebuild-4c-8g'
           code-branch: 'master'
           make-target: sanity-multi-kind
           onus: 2
@@ -176,7 +176,7 @@
       - 'voltha-periodic-test':
           name: 'periodic-voltha-etcd-test-2.7'
           pipeline-script: 'voltha-system-test-bbsim.groovy'
-          build-node: 'ubuntu16.04-basebuild-4c-8g'
+          build-node: 'ubuntu18.04-basebuild-4c-8g'
           code-branch: 'voltha-2.7'
           make-target: sanity-multi-kind
           onus: 2
@@ -208,7 +208,7 @@
 
       - 'voltha-periodic-test':
           name: 'nightly-voltha-DTflow-sanity-test'
-          build-node: 'ubuntu16.04-basebuild-4c-8g'
+          build-node: 'ubuntu18.04-basebuild-4c-8g'
           code-branch: 'master'
           make-target: sanity-kind-dt
           onus: 1
@@ -453,7 +453,7 @@
 - job-template:
     id: 'voltha-patch-test'
     name: 'verify_{project}_sanity-test{name-extension}'
-    build-node: 'ubuntu16.04-basebuild-4c-8g'
+    build-node: 'ubuntu18.04-basebuild-4c-8g'
     override-branch: '$GERRIT_BRANCH'
     sandbox: true
     build-timeout: 20