Fix check of the revision number in the resonse from API

In the test_router_interface_fip test module there was probably some
copy paste error which was checking if revision_number key exists in the
older response from the API then what was used in the assertion.
Now this is fixed.

TrivialFix

Change-Id: Ica10dfec9bb806c3dca2f0a2e0aff36006c9c092
1 file changed