The attribute that we need to be able to configure is deployment-timeout
This XML works. The value of 99999 for deployment-timeout is larger than required, but it is a number I put in the configuration to get it working.
<subsystem xmlns="urn:jboss:domain:deployment-scanner:1.1">
<deployment-scanner path="deployments" relative-to="jboss.server.base.dir" scan-interval="5000" deployment-timeout="99999"/>
</subsystem>