Fix for Jira:https://wso2.org/jira/browse/REGISTRY-2310

When there is circular referenced schemas,
the same schema file 'IS_CMM_MessageEnvelope_v2.xsd'
gets two source URIs.
1.file:///home/denuwanthi/G-reg/supportissues/CAPGRPDEV-91/G-reg/wso2greg-4.6.0/tmp/wsdl4429442587491522786/IS_CMM_MessageEnvelope_v2.xsd
2.file:/home/denuwanthi/G-reg/supportissues/CAPGRPDEV-91/G-reg/wso2greg-4.6.0/tmp/wsdl4429442587491522786/IS_CMM_MessageEnvelope_v2.xsd

Thus, duplication of schemas happens.
This happens when the uri contains 'file:'.