[Jenkins] Pull latest docker images.

docker.image('ogs6/gcc-gui:latest')# Please enter the commit message for your changes. Lines starting

scripts/jenkins/clang.groovy

@@ -18,7 +18,9 @@ node('docker') {
         dir('ogs') { checkout scm }
     }
 
-    docker.image('ogs6/clang-base:latest').inside(defaultDockerArgs) {
+    def image = docker.image('ogs6/clang-base:latest')
+    image.pull()
+    image.inside(defaultDockerArgs) {
         stage('Configure (Clang)') {
             configure.linux 'build', "${defaultCMakeOptions}"
         }

scripts/jenkins/coverage.groovy

@@ -7,7 +7,9 @@ node('docker') {
     stage('Checkout') { dir('ogs') { checkout scm } }
 
     stage('Build') {
-        docker.image('ogs6/gcc-base:latest').inside(defaultDockerArgs) {
+        def image = docker.image('ogs6/gcc-base:latest')
+        image.pull()
+        image.inside(defaultDockerArgs) {
             build this, 'build', '-DOGS_COVERAGE=ON',
                 'testrunner_coverage_cobertura ctest_coverage_cobertura'
         }

scripts/jenkins/docs.groovy

@@ -8,7 +8,9 @@ def build = new ogs.build()
 def post = new ogs.post()
 def helper = new ogs.helper()
 
-docker.image('ogs6/gcc-base:latest').inside() {
+def image = docker.image('ogs6/gcc-base:latest')
+image.pull()
+image.inside() {
     stage('Configure (Docs)') {
         configure.linux 'build', "${defaultCMakeOptions}"
     }

scripts/jenkins/gcc.groovy

@@ -8,7 +8,9 @@ def build = new ogs.build()
 def post = new ogs.post()
 def helper = new ogs.helper()
 
-docker.image('ogs6/gcc-gui:latest').inside(defaultDockerArgs) {
+def image = docker.image('ogs6/gcc-gui:latest')
+image.pull()
+image.inside(defaultDockerArgs) {
     stage('Configure (Linux-Docker)') {
         configure.linux 'build', "${defaultCMakeOptions}"
     }