Improved handling of jenkins uid and gid

Change-Id: Id03fd8887515bbc502dfffc22d7335fd7b95d18d
diff --git a/src/com/mirantis/mk/Common.groovy b/src/com/mirantis/mk/Common.groovy
index e6a890a..03e0c5e 100644
--- a/src/com/mirantis/mk/Common.groovy
+++ b/src/com/mirantis/mk/Common.groovy
@@ -61,6 +61,14 @@
 }
 
 /**
+ * Returns Jenkins user uid and gid in one list (in that order)
+ * Must be run from context of node
+ */
+def getJenkinsUserIds(){
+    return sh(script: "id -u && id -g", returnStdout: true).tokenize("\n")
+}
+
+/**
  *
  * Find credentials by ID
  *