Make correct render when dump Map object to YAML

Add correct YAML block ctructure when dump Map object to YAML

Before:
`parameters:
  _param: {cookiecutter_template_branch: release/proposed/2019.2.0,
    shared_reclass_branch: release/proposed/2019.2.0,
    apt_mk_version: "testing"}
`
After:
`parameters:
  _param:
    cookiecutter_template_branch: release/proposed/2019.2.0
    shared_reclass_branch: release/proposed/2019.2.0
    apt_mk_version: testing
`

Change-Id: Ifda304ba85369b25f5edcfdbdd479c7fdcf15c55
Related-Prod: PROD-30708
diff --git a/src/com/mirantis/mcp/Common.groovy b/src/com/mirantis/mcp/Common.groovy
index df3ef30..b83a714 100644
--- a/src/com/mirantis/mcp/Common.groovy
+++ b/src/com/mirantis/mcp/Common.groovy
@@ -1,10 +1,12 @@
 package com.mirantis.mcp
 
+import static org.yaml.snakeyaml.DumperOptions.FlowStyle.BLOCK
 import java.util.zip.GZIPInputStream
 import java.util.zip.GZIPOutputStream
 
 @Grab(group='org.yaml', module='snakeyaml', version='1.17')
 import org.yaml.snakeyaml.Yaml
+import org.yaml.snakeyaml.DumperOptions
 
 /**
  * https://issues.jenkins-ci.org/browse/JENKINS-26481
@@ -53,7 +55,10 @@
  */
 @NonCPS
 def dumpYAML(Map map) {
-  def yaml = new Yaml()
+  DumperOptions options = new DumperOptions()
+  options.setPrettyFlow(true)
+  options.setDefaultFlowStyle(DumperOptions.FlowStyle.BLOCK)
+  def yaml = new Yaml(options)
   return yaml.dump(map)
 }