Fix support for explicit disabling of syncing with the origin

Signed-off-by: Simon Hausmann <simon@lst.de>
diff --git a/contrib/fast-import/git-p4 b/contrib/fast-import/git-p4
index 815d8bb..ff56181 100755
--- a/contrib/fast-import/git-p4
+++ b/contrib/fast-import/git-p4
@@ -1028,6 +1028,8 @@
         self.knownBranches = {}
         self.initialParents = {}
         self.hasOrigin = gitBranchExists("origin") or gitBranchExists("origin/p4") or gitBranchExists("origin/p4/master")
+        if not self.syncWithOrigin:
+            self.hasOrigin = False
 
         if self.importIntoRemotes:
             self.refPrefix = "refs/remotes/p4/"