Add support for git wire protocol 2 on master and slave

Change-Id: I1c6912c127ade9f60dacf6df2754a963bd55cb95
diff --git a/jenkins-docker/master/gitconfig b/jenkins-docker/master/gitconfig
index 3995d4a..477b6b4 100644
--- a/jenkins-docker/master/gitconfig
+++ b/jenkins-docker/master/gitconfig
@@ -1,3 +1,5 @@
 [user]
 	name = Jenkins
 	email = jenkins@localhost
+[protocol]
+	version = 2
diff --git a/jenkins-docker/slave-debian/gitconfig b/jenkins-docker/slave-debian/gitconfig
index 3995d4a..477b6b4 100644
--- a/jenkins-docker/slave-debian/gitconfig
+++ b/jenkins-docker/slave-debian/gitconfig
@@ -1,3 +1,5 @@
 [user]
 	name = Jenkins
 	email = jenkins@localhost
+[protocol]
+	version = 2