Adding ability to run pipelines on jenkins slaves

The patch adds ability to run Groovy pipelines on specified
Jenkins slaves groupped by a label or standalone node name.

Change-Id: Ibdf6b3b87eefec00788b7d2b2ce67b3635a5dedc
diff --git a/cloud-deploy-pipeline.groovy b/cloud-deploy-pipeline.groovy
index 29d3007..9c3943b 100644
--- a/cloud-deploy-pipeline.groovy
+++ b/cloud-deploy-pipeline.groovy
@@ -31,6 +31,7 @@
  *   OPENSTACK_API_PROJECT      OpenStack project to connect to
  *   OPENSTACK_API_CLIENT       Versions of OpenStack python clients
  *   OPENSTACK_API_VERSION      Version of the OpenStack API (2/3)
+ *   SLAVE_NODE                 Lable or node name where the job will be run
 
  *   SALT_MASTER_CREDENTIALS    Credentials to the Salt API
  *  required for STACK_TYPE=physical
@@ -76,7 +77,13 @@
     def openstackCloud
 }
 
-node("python") {
+def slave_node = 'python'
+
+if (common.validInputParam(SLAVE_NODE)) {
+    slave_node = SLAVE_NODE
+}
+
+node(slave_node) {
     try {
         // Set build-specific variables
         venv = "${env.WORKSPACE}/venv"