ci(jenkins): reuse agents (4 less agents to be used) (#606)

Author: v1v

.ci/Jenkinsfile

@@ -4,7 +4,7 @@
 import co.elastic.matrix.*
 
 pipeline {
-  agent any
+  agent { label 'linux && immutable' }
   environment {
     BASE_DIR="src/github.com/elastic/apm-agent-python"
     PIPELINE_LOG_LEVEL='INFO'
@@ -26,7 +26,6 @@ pipeline {
   }
   stages {
     stage('Initializing'){
-      agent { label 'docker && linux && immutable' }
       options { skipDefaultCheckout() }
       environment {
         HOME = "${env.WORKSPACE}"
@@ -73,7 +72,6 @@ pipeline {
     Execute unit tests.
     */
     stage('Test') {
-      agent { label 'linux && immutable' }
       options {
         timeout(time: 1, unit: 'HOURS')
         skipDefaultCheckout()
@@ -96,7 +94,6 @@ pipeline {
       }
     }
     stage('Building packages') {
-      agent { label 'docker && linux && immutable' }
       options {
         timeout(time: 1, unit: 'HOURS')
         skipDefaultCheckout()
@@ -119,7 +116,6 @@ pipeline {
       }
     }
     stage('Release') {
-      agent { label 'linux && immutable' }
       options {
         skipDefaultCheckout()
         timeout(time: 12, unit: 'HOURS')

.ci/downstreamTests.groovy

@@ -11,7 +11,7 @@ it is need as field to store the results of the tests.
 @Field def pythonTasksGen
 
 pipeline {
-  agent any
+  agent { label 'linux && immutable' }
   environment {
     REPO="git@github.com:elastic/apm-agent-python.git"
     BASE_DIR="src/github.com/elastic/apm-agent-python"
@@ -41,7 +41,6 @@ pipeline {
     Checkout the code and stash it, to use it on other stages.
     */
     stage('Checkout') {
-      agent { label 'docker && linux && immutable' }
       options { skipDefaultCheckout() }
       steps {
         script {
@@ -64,7 +63,6 @@ pipeline {
     Execute unit tests.
     */
     stage('Test') {
-      agent { label 'linux && immutable' }
       options { skipDefaultCheckout() }
       steps {
         deleteDir()

.ci/linting.groovy

@@ -2,7 +2,7 @@
 @Library('apm@current') _
 
 pipeline {
-  agent any
+  agent { label 'linux && immutable' }
   options {
     buildDiscarder(logRotator(numToKeepStr: '20', artifactNumToKeepStr: '20', daysToKeepStr: '30'))
     timestamps()
@@ -17,7 +17,6 @@ pipeline {
   }
   stages {
     stage('Sanity checks') {
-      agent { label 'docker && linux && immutable' }
       environment {
         HOME = "${env.WORKSPACE}"
         PATH = "${env.PATH}:${env.WORKSPACE}/bin"

Jenkinsfile

@@ -11,7 +11,7 @@ it is need as field to store the results of the tests.
 @Field def pythonTasksGen
 
 pipeline {
-  agent any
+  agent { label 'linux && immutable' }
   environment {
     REPO = 'apm-agent-python'
     BASE_DIR = "src/github.com/elastic/${env.REPO}"
@@ -40,7 +40,6 @@ pipeline {
   }
   stages {
     stage('Initializing'){
-      agent { label 'docker && linux && immutable' }
       options { skipDefaultCheckout() }
       environment {
         HOME = "${env.WORKSPACE}"
@@ -87,7 +86,6 @@ pipeline {
     Execute unit tests.
     */
     stage('Test') {
-      agent { label 'linux && immutable' }
       options { skipDefaultCheckout() }
       steps {
         withGithubNotify(context: 'Test', tab: 'tests') {
@@ -113,7 +111,6 @@ pipeline {
       }
     }
     stage('Building packages') {
-      agent { label 'docker && linux && immutable' }
       options { skipDefaultCheckout() }
       environment {
         HOME = "${env.WORKSPACE}"
@@ -155,7 +152,6 @@ pipeline {
       }
     }
     stage('Release') {
-      agent { label 'linux && immutable' }
       options { skipDefaultCheckout() }
       environment {
         HOME = "${env.WORKSPACE}"