Property expansion stopped working in datasource connection-url

On 7.0.2.Final it was possible to use property expansion in the datasource connection-url, which is very useful for example when using embedded Apache Derby to specify that it should store the db in AS7's data directory.

The following worked fine on 7.0.2.Final, but stopped working in 7.1.0.CR1b (not tested on other 7.1.0.X versions):

<connection-url>jdbc:derby:${jboss.server.data.dir}/mydb;create=true</connection-url>

Without property expansion, and with property expansion not available for system-properties either (see AS7-2579) it is rather difficult to make sure the db for an embedded database is saved within the AS7 data directory.