transaction: fix file descriptor leak for journal.backupfiles

The journal.backupfiles descriptor wasn't being closed. This resulted in
hgsubversion test runs having a bagillion descriptors open, which crashed on
platforms with low open file limits (like OSX).

mercurial/transaction.py

@@ -220,6 +220,7 b' class transaction(object):'
         if self.count != 0:
             return
         self.file.close()
+        self.backupsfile.close()
         self.entries = []
         if self.after:
             self.after()
@@ -243,6 +244,7 b' class transaction(object):'
         self.count = 0
         self.usages = 0
         self.file.close()
+        self.backupsfile.close()
 
         if self.onabort is not None:
             self.onabort()