solve netconf mock issues in Fluorine

Fluorine changed the netconf EXI compression format interpreter library from openEXI to EXIficient.
This results in backward compatibility issues between the Fluorine controller and testtool pre-Fluorine versions (i.e. <1.5.0)

FD.io Hoenycomb is also affected since it is still based on Opendaylight versions prior to Fluorine.