CI: Escape backslashes in printenv/sort/tr

Change-Id: I52be64c8f6af2bbe15148a856d1f10cb113e1e94
(cherry picked from commit c6558e09)

tests/CI/gates.jenkinsfile

@@ -100,7 +100,7 @@ pipeline {
 						withCredentials([usernamePassword(credentialsId: "${JENKINS_GERRIT_CREDS}",
 							passwordVariable: 'GERRIT_USER_PW', usernameVariable: 'GERRIT_USER_NAME')]) {
 
-							sh "printenv -0 | sort -z | tr '\0' '\n'"
+							sh "printenv -0 | sort -z | tr '\\0' '\\n'"
 
 							checkout scm: [$class: 'GitSCM',
 								branches: [[name: env.GERRIT_BRANCH ]],

tests/CI/periodics-daily.jenkinsfile

@@ -43,7 +43,7 @@ pipeline {
 
 					stage ("Checkout") {
 						sh "sudo chown -R jenkins:users ."
-						sh "printenv -0 | sort -z | tr '\0' '\n'"
+						sh "printenv -0 | sort -z | tr '\\0' '\\n'"
 						sh "sudo tests/CI/setupJenkinsEnvironment.sh"
 					}
 

tests/CI/ref_debug.jenkinsfile

@@ -43,7 +43,7 @@ pipeline {
 
 					stage ("Checkout") {
 						sh "sudo chown -R jenkins:users ."
-						sh "printenv -0 | sort -z | tr '\0' '\n'"
+						sh "printenv -0 | sort -z | tr '\\0' '\\n'"
 						sh "sudo tests/CI/setupJenkinsEnvironment.sh"
 					}
 

tests/CI/unittests.jenkinsfile

@@ -100,7 +100,7 @@ pipeline {
 						withCredentials([usernamePassword(credentialsId: "${JENKINS_GERRIT_CREDS}",
 							passwordVariable: 'GERRIT_USER_PW', usernameVariable: 'GERRIT_USER_NAME')]) {
 
-							sh "printenv -0 | sort -z | tr '\0' '\n'"
+							sh "printenv -0 | sort -z | tr '\\0' '\\n'"
 
 							checkout scm: [$class: 'GitSCM',
 								branches: [[name: env.GERRIT_BRANCH ]],