<?xml version="1.0" encoding="UTF-8"?>
<scr:component xmlns:scr="http://www.osgi.org/xmlns/scr/v1.1.0" immediate="false" name="Activemq Connector Service">
   <implementation class="uk.ac.diamond.daq.activemq.connector.ActivemqConnectorService"/>
    <service>
      <provide interface="org.eclipse.scanning.api.event.IEventConnectorService"/>
   </service>
    <reference bind="setMarshaller" cardinality="1..1" interface="org.eclipse.dawnsci.analysis.api.persistence.IJSonMarshaller" name="IJSonMarshaller" policy="static"/>
</scr:component>

<?xml version="1.0" encoding="UTF-8"?>
<scr:component xmlns:scr="http://www.osgi.org/xmlns/scr/v1.1.0" immediate="false" name="Activemq Connector Service">
   <implementation class="uk.ac.diamond.daq.activemq.connector.ActivemqConnectorService"/>
    <service>
      <provide interface="org.eclipse.scanning.api.event.IEventConnectorService"/>
   </service>
    <reference bind="setMarshaller" cardinality="0..1" interface="org.eclipse.dawnsci.analysis.api.persistence.IJSonMarshaller" name="IJSonMarshaller" policy="static"/>
</scr:component>

Change cardinality of ActivemqConnectorService to 0..1 it is not actually required
Change cardinality of ActivemqConnectorService to 0..1 it is not actually required

This allows the service to start when no implementation of
ActivemqConnectorService is avaliable to OSGi