Parametrize usage of git global config

Since related issue is sporadic, disable usage of global
config and make it optional.

Change-Id: I5edffbdc0e845ea600a77c7714cfcf2ec1e988bc
Related-Prod: PROD-28160 (PROD:28160)
diff --git a/src/com/mirantis/mk/Git.groovy b/src/com/mirantis/mk/Git.groovy
index d20c159..1564fec 100644
--- a/src/com/mirantis/mk/Git.groovy
+++ b/src/com/mirantis/mk/Git.groovy
@@ -99,12 +99,17 @@
  *
  * @param path            Path to the git repository
  * @param message         A commit message
+ * @param global          Use global config
  */
-def commitGitChanges(path, message, gitEmail='jenkins@localhost', gitName='jenkins-slave') {
+def commitGitChanges(path, message, gitEmail='jenkins@localhost', gitName='jenkins-slave', global=false) {
     def git_cmd
+    def global_arg = ''
+    if (global) {
+        global_arg = '--global'
+    }
     dir(path) {
-        sh "git config --global user.email '${gitEmail}'"
-        sh "git config --global user.name '${gitName}'"
+        sh "git config ${global_arg} user.email '${gitEmail}'"
+        sh "git config ${global_arg} user.name '${gitName}'"
 
         sh(
             script: 'git add -A',