Properties set on the root directory never conflict.

Short description:

Properties added to the root directory of a working copy (".") never conflicts
unlike properties set on regular below root directory.
This is 100% reproducible on a Debian sid box running debian packaged Subversion
1.4.4.

Step to Reproduce:
$ svnadmin create testprop
$ svn co file://`pwd`/testprop a
Checked out revision 0.
$ svn co file://`pwd`/testprop b
Checked out revision 0.
$ cd a
$ svn propset 'prop' 'value 1' .
property 'prop' set on '.'
$ svn ci -m "r1"
Sending        .

Committed revision 1.
$ cd ../b
$ svn propset 'prop' 'value 2' .
property 'prop' set on '.'
$ svn ci -m "r2"
Sending        .

Committed revision 2.

The last commit operation should have failed with an "out of date" error message.

Doing the same operation on a below-root regular directory works as intended:
$ svnadmin create testprop
$ svn co file://`pwd`/testprop
Checked out revision 0.
$ svn co file://`pwd`/testprop a
Checked out revision 0.
$ svn co file://`pwd`/testprop b
Checked out revision 0.
$ cd a
$ svn mkdir dir
A         dir
$ svn ci -m "r1"
Adding         dir

Committed revision 1.
$ svn propset 'prop' 'value 1' dir
property 'prop' set on 'dir'
$ svn ci -m "r2"
Sending        dir

Committed revision 2.
$ cd ../b
$ svn up -r1  
A    dir
Updated to revision 1.
$ svn propset 'prop' 'conflict' dir
property 'prop' set on 'dir'
$ svn ci -m "r3"
Sending        dir
svn: Commit failed (details follow):
svn: Out of date: '/dir' in transaction '2-1'

Test-case:
#!/bin/sh

echo "create the svn repository"
svnadmin create testprop
svn co file://`pwd`/testprop a
svn co file://`pwd`/testprop b
echo "going into working copy a"
cd a
svn propset 'prop' 'value 1' .
echo "commit r1"
svn ci -m "r1"
echo "going into working copy b"
cd ../b
svn propset 'prop' 'value 2' .
echo "commit r2"
svn ci -m "r2"

Original issue reported by masterzen666