fix: use sh instead of docker plugin

jenkins/Jenkinsfile

@@ -19,9 +19,7 @@ def sharedPackageVersion
 
 // Docker images
 def appImage
-def appTestsImage
 def contractsImage
-def contractsTestsImage
 def contractsProviderImage
 def pinnerImage
 
@@ -113,7 +111,6 @@ pipeline {
         stage('TEST CONTRACTS') {
           steps {
             script {
-              try {
               def ganacheTestPort = sh(script: "bash ./jenkins/hash_build_properties.sh ${BRANCH_NAME} ${BUILD_NUMBER} | xargs bash ./jenkins/map_to_thousand.sh", returnStdout: true).trim()
 
               def ganacheTestImage = docker.build(
@@ -122,14 +119,7 @@ pipeline {
                 ./"
               )
 
-                sh 'docker network create --driver bridge concordia_ganache_test_network || true'
-
-                ganacheTestImage.withRun("""-d -p 6${ganacheTestPort}:8546 \
-                --env-file=./jenkins/env/ganache.test.jenkins.env \
-                --name concordia-ganache-test-6${ganacheTestPort} \
-                --net=concordia_ganache_test_network""") { concordiaGanacheTest ->
-
-                  contractsTestsImage = docker.build(
+              docker.build(
                 "ecentrics/concordia-contracts-tests:${sanitizedBranchName}-v${contractsPackageVersion}-b${BUILD_NUMBER}-tests",
                 "-f docker/concordia-contracts/Dockerfile \
                 ./ \
@@ -137,13 +127,22 @@ pipeline {
                 --build-arg TZ=Europe/Athens"
               )
 
-                  contractsTestsImage.run("""--rm \
+              sh 'docker network create --driver bridge concordia_ganache_test_network || true'
+
+              ganacheTestImage.withRun("""-d -p 6${ganacheTestPort}:8546 \
+                --env-file=./jenkins/env/ganache.test.jenkins.env \
+                --name concordia-ganache-test-6${ganacheTestPort} \
+                --net=concordia_ganache_test_network""") { concordiaGanacheTest ->
+
+                try {
+                   sh """docker run \
+                     --rm \
                      -v ecentrics_janus_common:/mnt/concordia/test-reports/ \
                      --env-file=./jenkins/env/contracts.test.jenkins.env \
                      -e WEB3_HOST=concordia-ganache-test-6${ganacheTestPort} \
                      -e WEB3_PORT=6${ganacheTestPort} \
-                  --net=concordia_ganache_test_network""")
-                }
+                     --net=concordia_ganache_test_network \
+                     ecentrics/concordia-contracts-tests:${sanitizedBranchName}-v${contractsPackageVersion}-b${BUILD_NUMBER}-tests"""
                 } catch (e) {
                   error('Some tests failed!')
                   error('Aborting the build.')
@@ -155,6 +154,7 @@ pipeline {
               }
             }
           }
+        }
 
         stage('TEST APP') {
           steps {