To answer my own question. I just needed to add a binding library for opencmis:
<dependency>
<groupId>org.apache.chemistry.opencmis</groupId>
<artifactId>chemistry-opencmis-client-bindings</artifactId>
<version>${version.opencmis}</version>
</dependency>
And then add this to initialization:
parameter.put(SessionParameter.WEBSERVICES_PORT_PROVIDER_CLASS, CXFPortProvider.class.getName());