jobs/common: added cleanup function restoring unstaged changes

with the script updating the source revisions some unstaged
changes reside in the repository. A following job will be unable
to succeed as the clone will fail. Thus, adding this function
which now can be used in the specific jobs.

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

jobs/Jenkinsfile_Common

@@ -144,6 +144,13 @@ def gitCheckout(gitUrl, branchTag, repoDir, hasSubmodules) {
     println "Last 3 git commits:\n-----------------------------\n${gitHistory}"
   }
 }
+//-----------------------------------------------------------------------------
+def cleanupRepository(repoDir) {
+  println "cleanup repository (e.g. temporary source revision updates)..."
+  dir("${repoDir}") {
+    sh("git restore .")
+  }
+}
 
 
 //-----------------------------------------------------------------------------