Enable "sync -c" default for repo

There's no need to fetch every single branch

Change-Id: I48861c2b46e5d9d94c478fa78e2724546f71ddf1
diff --git a/default.xml b/default.xml
index 114873d..1ce0add 100644
--- a/default.xml
+++ b/default.xml
@@ -13,6 +13,7 @@
 
   <default revision="refs/heads/jellybean"
            remote="github"
+           sync-c="true"
            sync-j="4" />
 
   <project path="build" name="CyanogenMod/android_build">