FS C tests: remove backend-dependent early out from tests that don't depend on
backend implementation details.

* subversion/tests/libsvn_fs_fs/fs-fs-pack-test.c
  (create_packed_filesystem): Only munge the format file for FSFS.
  (read_packed_fs, commit_packed_fs, get_set_revprop_packed_fs,
   get_set_large_revprop_packed_fs, get_set_huge_revprop_packed_fs,
   recover_fully_packed, file_hint_at_shard_boundary, test_info,
   pack_shard_size_one, get_set_multiple_huge_revprops_packed_fs):
      As above.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1515378 13f79535-47bb-0310-9956-ffa450edef68