ZP-455 #comment do not send empty responses in case of a non-ok sync status

git-svn-id: http://svn.berlios.de/svnroot/repos/z-push/trunk@1752 b7dd7b3b-3a3c-0410-9da9-bee62a6cc5b5
ZP-458 #comment SyncCollection should not remove old states anymore. This is only done by regular sync operations now.

git-svn-id: http://svn.berlios.de/svnroot/repos/z-push/trunk@1753 b7dd7b3b-3a3c-0410-9da9-bee62a6cc5b5