Remove workarounds for ODL bugs from ietf-routing YANG models (RFC 8349)

new ietf-routing@2018-03-13 yang models revealed bugs which caused failures during model build:

• naming conflicts for two classes generated in the same package. see https://jira.opendaylight.org/browse/MDSAL-332
• actions cannot be processed. see https://jira.opendaylight.org/browse/YANGTOOLS-841 and https://jira.opendaylight.org/browse/MDSAL-300
• special characters in enums are not processed correctly. see https://jira.opendaylight.org/browse/MDSAL-309
• submodule is not processed correctly YANGTOOLS-876 (resolved in yangtools 2.0.4, we can remove the workaround in hc2vpp-ietf-ipv6-unicast-routing when honeycomb migrates to the newer version of yangtools)

For now these bugs were resolved by renaming or commenting out affected sections of routing models. Needs to be corrected once bugs are fixed.