git-p4: unshelve into refs/remotes/p4-unshelved, not refs/remotes/p4/unshelved

The branch detection code looks for branches under refs/remotes/p4/...
and can end up getting confused if there are unshelved changes in
there as well. This happens in the function p4BranchesInGit().

Instead, put the unshelved changes into refs/remotes/p4-unshelved/<N>.

Signed-off-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git-p4.py b/git-p4.py
index 5701bad..76c18a2 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -3956,7 +3956,8 @@ def __init__(self):
         ]
         self.verbose = False
         self.noCommit = False
-        self.destbranch = "refs/remotes/p4/unshelved"
+        self.destbranch = "refs/remotes/p4-unshelved"
+        self.origin = "p4/master"
 
     def renameBranch(self, branch_name):
         """ Rename the existing branch to branch_name.N