Fix FSFS format 7 commit on Windows.

* subversion/libsvn_fs_fs/index.c
  (svn_fs_fs__l2p_index_create,
   svn_fs_fs__p2l_index_create): Close proto-index file handles right after
                                 usage such that we can delete the txn dir
                                 on Windows.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1547079 13f79535-47bb-0310-9956-ffa450edef68