jenkins: using build_user and sshagent for sync-ing yocto downloads

our AD user 'build_user' was adapted for having an SSH key. Jenkins
was configured to have this user with its key under Credentials so
that the sshagent could be used.
This way seems to be the most secure way performing ssh connections.

BugzID: 71491

Signed-off-by: Marc Mattmueller <marc.mattmueller@netmodule.com>

Jenkinsfile

@@ -27,7 +27,7 @@ pipeline {
     SUBMODULE_VERION_FILE = "submodule_revisions"
     AUTOREV_VERSION_FILE = "autorev_revisions.inc"
 
-    BINARY_STORAGE_URL = "http://nmrepo.netmodule.intranet/src/yocto-downloads/"
+    BINARY_STORAGE_URL = "http://nmrepo.netmodule.intranet/src/yocto-downloads"
   }
 
   options {
@@ -173,14 +173,13 @@ def cleanupDistroVersion() {
 
 def syncSources(src, dst) {
   def hasSrcUrl = (src.contains("http"))
-  def syncCmd = "rsync -avz -e \"ssh\""
   def from = src
   def to = dst
 
   // convert the URL into ssh syntax:
   def url = (hasSrcUrl) ? src : dst
   String[] repoParts = url.split("//")[1].split("/")
-  repoParts[0] = "jenkins@" + repoParts[0] + ":/repo/repo"
+  repoParts[0] = "build_user@" + repoParts[0] + ":/repo/repo"
   sshSrc = repoParts.join("/")
 
   if(hasSrcUrl) {
@@ -191,7 +190,10 @@ def syncSources(src, dst) {
     println "putting data to server..."
     to = sshSrc
   }
-  sh(script: "${syncCmd} ${from}/ ${to}")
+
+  sshagent (credentials: ['7767e711-08a4-4c71-b080-197253dd7392']) {
+    sh "rsync -auvz --ignore-existing -e \"ssh\" ${from}/* ${to}"
+  }
 }