On the fsfs-format7 branch: fix root noderevs being returned from the
container.

* subversion/libsvn_fs_fs/noderevs.c
  (svn_fs_fs__noderevs_get): default copyroot_rev is 0 instead of -1

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1477187 13f79535-47bb-0310-9956-ffa450edef68