no-op prop change not preserved across dump/load

svnadmin create repo
svnmucc -mm -U file://`pwd`/repo mkdir A propset p v A
svnmucc -mm -U file://`pwd`/repo propset p v A

The log of r2 shows status 'M' for the path '/A', this is true for FSFS, BDB and FSX.

svnadmin create repo2
svnadmin dump repo | svnadmin load repo2

The log of r2 after a dump/load does not show '/A' as status 'M'.

Note that if the first repo has 'enable-rep-sharing=false' then the 'M' status does get preserved by the dump/load.

See svnadmin_tests.py:dump_no_op_prop_change.